fix(chat,todo): show sent chat messages immediately + kanban drag-and-drop reorder

チャット送信の即時表示とKanbanのDnD並べ替えを修正。

- chat: 送信成功時に返却メッセージを楽観的にローカルへ先頭追加(SSE到着前でも即表示、idで重複排除)。setSending(false) をレスポンス処理後に移動し二重送信窓を縮小。
- todo: TodoService.reorderItems(projectId, columnId, itemIds[]) を追加(1トランザクションでカラム内を再採番、メンバーシップ+同プロジェクト検証、活動ログ/SSEは1件)。POST /todos/items/reorder を追加。
- KanbanBoard: カード単位のドロップターゲット(ポインタYで前/後挿入)+カラム空き領域は末尾追加。楽観的にorderIndex/columnIdを更新しrenderをorderIndexでソート(即時反映)、失敗時はエラー表示+再取得で巻き戻し。ドラッグ直後の誤クリック(ダイアログ誘起)をdragEndタイムスタンプで抑制。空の並べ替えはSSE/ログを出さない。

components/todo/KanbanBoard.tsx

@@ -1,6 +1,6 @@
 'use client';
 
-import { useCallback, useState, type DragEvent } from 'react';
+import { useCallback, useRef, useState, type DragEvent } from 'react';
 import type { TodoColumn, TodoItem } from '@/lib/types';
 import type { ProjectMemberWithUser } from '@/repositories/ProjectMemberRepository';
 import { TodoDialog } from '@/components/todo/TodoDialog';
@@ -11,6 +11,11 @@ const PRIORITY_COLORS: Record<string, string> = {
   low: 'bg-gray-100 dark:bg-gray-700 text-gray-600 dark:text-gray-300',
 };
 
+/** 同一 orderIndex は id で安定ソート(createdAt 同着対策) */
+function byOrder(a: TodoItem, b: TodoItem): number {
+  return a.orderIndex - b.orderIndex || a.id - b.id;
+}
+
 export function KanbanBoard({
   projectId,
   columns,
@@ -25,6 +30,9 @@ export function KanbanBoard({
   const [items, setItems] = useState<TodoItem[]>(initialItems);
   const [draggingId, setDraggingId] = useState<number | null>(null);
   const [selectedItem, setSelectedItem] = useState<TodoItem | null>(null);
+  const [error, setError] = useState<string | null>(null);
+  // ドラッグ直後の誤クリック(ダイアログを開く)を抑制するためのタイムスタンプ
+  const lastDragEndAtRef = useRef(0);
 
   const reload = useCallback(async () => {
     const res = await fetch(`/api/projects/${projectId}/todos/items`);
@@ -40,27 +48,84 @@ export function KanbanBoard({
     e.dataTransfer.setData('text/plain', String(itemId));
   }
 
+  function applyReorder(
+    prev: TodoItem[],
+    destColumnId: number,
+    newOrderIds: number[]
+  ): TodoItem[] {
+    const order = new Map(newOrderIds.map((id, idx) => [id, idx]));
+    return prev.map((i) =>
+      order.has(i.id)
+        ? { ...i, columnId: destColumnId, orderIndex: order.get(i.id)! }
+        : i
+    );
+  }
+
+  function columnItemIds(columnId: number, excludeId?: number): number[] {
+    return items
+      .filter((i) => i.columnId === columnId && i.id !== excludeId)
+      .sort((a, b) => a.orderIndex - b.orderIndex || a.id - b.id)
+      .map((i) => i.id);
+  }
+
+  async function persistReorder(
+    destColumnId: number,
+    newOrderIds: number[]
+  ): Promise<void> {
+    setItems((prev) => applyReorder(prev, destColumnId, newOrderIds));
+    setError(null);
+    try {
+      const res = await fetch(
+        `/api/projects/${projectId}/todos/items/reorder`,
+        {
+          method: 'POST',
+          headers: { 'Content-Type': 'application/json' },
+          body: JSON.stringify({
+            columnId: destColumnId,
+            itemIds: newOrderIds,
+          }),
+        }
+      );
+      if (!res.ok) {
+        setError('並べ替えに失敗しました');
+      }
+    } catch {
+      setError('並べ替えに失敗しました');
+    } finally {
+      await reload();
+    }
+    setDraggingId(null);
+  }
+
+  // カラムの空き領域へのドロップ = 末尾に追加
   function onDrop(e: DragEvent<HTMLElement>, column: TodoColumn) {
     e.preventDefault();
     const itemId = Number(e.dataTransfer.getData('text/plain'));
-    if (!itemId) return;
-    const item = items.find((i) => i.id === itemId);
-    if (!item || item.columnId === column.id) {
+    if (!itemId) {
       setDraggingId(null);
       return;
     }
-    // 楽観的にローカル更新したあとAPIで移動(失敗時は再取得で巻き戻す)
-    setItems((prev) =>
-      prev.map((i) => (i.id === itemId ? { ...i, columnId: column.id } : i))
-    );
-    fetch(`/api/projects/${projectId}/todos/items/${itemId}`, {
-      method: 'PATCH',
-      headers: { 'Content-Type': 'application/json' },
-      body: JSON.stringify({ columnId: column.id, orderIndex: 0 }),
-    })
-      .catch(() => undefined)
-      .finally(() => reload());
-    setDraggingId(null);
+    const newOrderIds = [...columnItemIds(column.id, itemId), itemId];
+    void persistReorder(column.id, newOrderIds);
+  }
+
+  // カード上へのドロップ = ポインタ位置で前後に挿入
+  function dropOnItem(e: DragEvent<HTMLElement>, target: TodoItem) {
+    e.preventDefault();
+    e.stopPropagation();
+    const itemId = Number(e.dataTransfer.getData('text/plain'));
+    if (!itemId || itemId === target.id) {
+      setDraggingId(null);
+      return;
+    }
+    const rect = e.currentTarget.getBoundingClientRect();
+    const before = e.clientY - rect.top < rect.height / 2;
+    const ordered = columnItemIds(target.columnId, itemId);
+    const insertAt = before
+      ? ordered.indexOf(target.id)
+      : ordered.indexOf(target.id) + 1;
+    ordered.splice(insertAt, 0, itemId);
+    void persistReorder(target.columnId, ordered);
   }
 
   async function addTask(columnId: number, title: string) {
@@ -82,116 +147,142 @@ export function KanbanBoard({
   }
 
   return (
-    <div className="flex gap-4 overflow-x-auto pb-4" data-testid="kanban-board">
-      {columns.map((column) => {
-        const colItems = items.filter((i) => i.columnId === column.id);
-        return (
-          <section
-            key={column.id}
-            className="w-64 shrink-0 rounded-lg bg-gray-100 dark:bg-gray-700 p-3"
-            onDragOver={(e) => e.preventDefault()}
-            onDrop={(e) => onDrop(e, column)}
-            data-testid={`kanban-column-${column.id}`}
-            data-column-id={column.id}
-          >
-            <h2 className="mb-2 text-sm font-semibold text-gray-700 dark:text-gray-200">
-              {column.name} ({colItems.length})
-            </h2>
-            <ul className="space-y-2">
-              {colItems.map((item) => {
-                const tags = item.tags
-                  ?.split(',')
-                  .map((t) => t.trim())
-                  .filter(Boolean);
-                const assignee = members.find(
-                  (m) => m.user.id === item.assigneeId
-                );
-                return (
-                  <li
-                    key={item.id}
-                    draggable
-                    onDragStart={(e) => onDragStart(e, item.id)}
-                    onClick={() => setSelectedItem(item)}
-                    className={`cursor-grab rounded border bg-white dark:bg-gray-800 p-2 shadow-sm ${
-                      draggingId === item.id ? 'opacity-50' : ''
-                    } ${item.completedAt ? 'opacity-60 line-through' : ''}`}
-                    data-testid={`todo-card-${item.id}`}
-                  >
-                    <div className="flex items-start justify-between gap-2">
-                      <span
-                        className="text-sm hover:text-blue-600 hover:underline"
-                        data-testid={`todo-open-${item.id}`}
-                      >
-                        {item.title}
-                      </span>
-                      <button
-                        type="button"
-                        onClick={(e) => {
-                          e.stopPropagation();
-                          toggleComplete(item.id);
-                        }}
-                        className="text-xs text-blue-600 hover:underline"
-                        data-testid={`todo-complete-${item.id}`}
-                      >
-                        {item.completedAt ? '戻す' : '完了'}
-                      </button>
-                    </div>
-                    <div className="mt-1 flex flex-wrap items-center gap-1">
-                      <span
-                        className={`rounded px-1.5 py-0.5 text-xs ${
-                          PRIORITY_COLORS[item.priority] ??
-                          PRIORITY_COLORS.normal
-                        }`}
-                      >
-                        {item.priority}
-                      </span>
-                      {item.dueDate && (
-                        <span className="text-xs text-gray-500 dark:text-gray-400">
-                          期限: {item.dueDate}
-                        </span>
-                      )}
-                      {item.startDate && (
-                        <span className="text-xs text-gray-400 dark:text-gray-500">
-                          開始: {item.startDate}
-                        </span>
-                      )}
-                      {assignee && (
-                        <span className="text-xs text-gray-500 dark:text-gray-400">
-                          @{assignee.user.name}
-                        </span>
-                      )}
-                    </div>
-                    {tags && tags.length > 0 && (
-                      <div className="mt-1 flex flex-wrap gap-1">
-                        {tags.map((t) => (
-                          <span
-                            key={t}
-                            className="rounded bg-gray-100 dark:bg-gray-700 px-1.5 py-0.5 text-[10px] text-gray-600 dark:text-gray-300"
-                          >
-                            {t}
-                          </span>
-                        ))}
-                      </div>
-                    )}
-                  </li>
-                );
-              })}
-            </ul>
-            <NewTaskInput onAdd={(title) => addTask(column.id, title)} />
-          </section>
-        );
-      })}
-
-      {selectedItem && (
-        <TodoDialog
-          projectId={projectId}
-          item={selectedItem}
-          members={members}
-          onClose={() => setSelectedItem(null)}
-          onSaved={reload}
-        />
+    <>
+      {error && (
+        <p
+          className="mb-2 text-sm text-red-600"
+          role="alert"
+          data-testid="kanban-error"
+        >
+          {error}
+        </p>
       )}
-    </div>
+      <div
+        className="flex gap-4 overflow-x-auto pb-4"
+        data-testid="kanban-board"
+      >
+        {columns.map((column) => {
+          const colItems = items
+            .filter((i) => i.columnId === column.id)
+            .sort(byOrder);
+          return (
+            <section
+              key={column.id}
+              className="w-64 shrink-0 rounded-lg bg-gray-100 dark:bg-gray-700 p-3"
+              onDragOver={(e) => e.preventDefault()}
+              onDrop={(e) => onDrop(e, column)}
+              data-testid={`kanban-column-${column.id}`}
+              data-column-id={column.id}
+            >
+              <h2 className="mb-2 text-sm font-semibold text-gray-700 dark:text-gray-200">
+                {column.name} ({colItems.length})
+              </h2>
+              <ul className="space-y-2">
+                {colItems.map((item) => {
+                  const tags = item.tags
+                    ?.split(',')
+                    .map((t) => t.trim())
+                    .filter(Boolean);
+                  const assignee = members.find(
+                    (m) => m.user.id === item.assigneeId
+                  );
+                  return (
+                    <li
+                      key={item.id}
+                      draggable
+                      onDragStart={(e) => onDragStart(e, item.id)}
+                      onDragEnd={() => {
+                        lastDragEndAtRef.current = Date.now();
+                        setDraggingId(null);
+                      }}
+                      onDragOver={(e) => e.preventDefault()}
+                      onDrop={(e) => dropOnItem(e, item)}
+                      onClick={() => {
+                        // ドラッグ直後の誤クリックでダイアログが開かないようにする
+                        if (Date.now() - lastDragEndAtRef.current < 300) return;
+                        setSelectedItem(item);
+                      }}
+                      className={`cursor-grab rounded border bg-white dark:bg-gray-800 p-2 shadow-sm ${
+                        draggingId === item.id ? 'opacity-50' : ''
+                      } ${item.completedAt ? 'opacity-60 line-through' : ''}`}
+                      data-testid={`todo-card-${item.id}`}
+                    >
+                      <div className="flex items-start justify-between gap-2">
+                        <span
+                          className="text-sm hover:text-blue-600 hover:underline"
+                          data-testid={`todo-open-${item.id}`}
+                        >
+                          {item.title}
+                        </span>
+                        <button
+                          type="button"
+                          onClick={(e) => {
+                            e.stopPropagation();
+                            toggleComplete(item.id);
+                          }}
+                          className="text-xs text-blue-600 hover:underline"
+                          data-testid={`todo-complete-${item.id}`}
+                        >
+                          {item.completedAt ? '戻す' : '完了'}
+                        </button>
+                      </div>
+                      <div className="mt-1 flex flex-wrap items-center gap-1">
+                        <span
+                          className={`rounded px-1.5 py-0.5 text-xs ${
+                            PRIORITY_COLORS[item.priority] ??
+                            PRIORITY_COLORS.normal
+                          }`}
+                        >
+                          {item.priority}
+                        </span>
+                        {item.dueDate && (
+                          <span className="text-xs text-gray-500 dark:text-gray-400">
+                            期限: {item.dueDate}
+                          </span>
+                        )}
+                        {item.startDate && (
+                          <span className="text-xs text-gray-400 dark:text-gray-500">
+                            開始: {item.startDate}
+                          </span>
+                        )}
+                        {assignee && (
+                          <span className="text-xs text-gray-500 dark:text-gray-400">
+                            @{assignee.user.name}
+                          </span>
+                        )}
+                      </div>
+                      {tags && tags.length > 0 && (
+                        <div className="mt-1 flex flex-wrap gap-1">
+                          {tags.map((t) => (
+                            <span
+                              key={t}
+                              className="rounded bg-gray-100 dark:bg-gray-700 px-1.5 py-0.5 text-[10px] text-gray-600 dark:text-gray-300"
+                            >
+                              {t}
+                            </span>
+                          ))}
+                        </div>
+                      )}
+                    </li>
+                  );
+                })}
+              </ul>
+              <NewTaskInput onAdd={(title) => addTask(column.id, title)} />
+            </section>
+          );
+        })}
+
+        {selectedItem && (
+          <TodoDialog
+            projectId={projectId}
+            item={selectedItem}
+            members={members}
+            onClose={() => setSelectedItem(null)}
+            onSaved={reload}
+          />
+        )}
+      </div>
+    </>
   );
 }