feat: initial commit - opencode spec-driven development boilerplate

Converted from Claude Code boilerplate to opencode:
- CLAUDE.md -> AGENTS.md (opencode instructions)
- .claude/settings.json -> opencode.json (permissions schema)
- .claude/agents/ -> .opencode/agent/ (subagents with mode: subagent)
- .claude/commands/ -> .opencode/command/ (slash commands with )
- .claude/skills/ -> .opencode/skills/ (7 skills, removed allowed-tools)
- DevContainer updated to install opencode
- All .claude/ paths and Claude Code references updated

src/example.test.ts

@@ -0,0 +1,93 @@
+import { describe, it, expect } from 'vitest';
+import { add, subtract, multiply, divide } from './example';
+
+describe('Math operations', () => {
+  describe('add', () => {
+    it('正の数を足すと正しい結果が返る', () => {
+      // Given: 準備
+      const a = 2;
+      const b = 3;
+
+      // When: 実行
+      const result = add(a, b);
+
+      // Then: 検証
+      expect(result).toBe(5);
+    });
+
+    it('負の数を足すと正しい結果が返る', () => {
+      // Given: 準備
+      const a = -2;
+      const b = 3;
+
+      // When: 実行
+      const result = add(a, b);
+
+      // Then: 検証
+      expect(result).toBe(1);
+    });
+  });
+
+  describe('subtract', () => {
+    it('正の数を引くと正しい結果が返る', () => {
+      // Given: 準備
+      const a = 5;
+      const b = 3;
+
+      // When: 実行
+      const result = subtract(a, b);
+
+      // Then: 検証
+      expect(result).toBe(2);
+    });
+  });
+
+  describe('multiply', () => {
+    it('正の数をかけると正しい結果が返る', () => {
+      // Given: 準備
+      const a = 2;
+      const b = 3;
+
+      // When: 実行
+      const result = multiply(a, b);
+
+      // Then: 検証
+      expect(result).toBe(6);
+    });
+
+    it('0をかけると0が返る', () => {
+      // Given: 準備
+      const a = 5;
+      const b = 0;
+
+      // When: 実行
+      const result = multiply(a, b);
+
+      // Then: 検証
+      expect(result).toBe(0);
+    });
+  });
+
+  describe('divide', () => {
+    it('正の数で割ると正しい結果が返る', () => {
+      // Given: 準備
+      const a = 6;
+      const b = 3;
+
+      // When: 実行
+      const result = divide(a, b);
+
+      // Then: 検証
+      expect(result).toBe(2);
+    });
+
+    it('0で割るとエラーをスローする', () => {
+      // Given: 準備
+      const a = 5;
+      const b = 0;
+
+      // When/Then: 実行と検証
+      expect(() => divide(a, b)).toThrow('Division by zero is not allowed');
+    });
+  });
+});

src/example.ts

@@ -0,0 +1,18 @@
+export function add(a: number, b: number): number {
+  return a + b;
+}
+
+export function subtract(a: number, b: number): number {
+  return a - b;
+}
+
+export function multiply(a: number, b: number): number {
+  return a * b;
+}
+
+export function divide(a: number, b: number): number {
+  if (b === 0) {
+    throw new Error('Division by zero is not allowed');
+  }
+  return a / b;
+}