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

package.json

@@ -0,0 +1,44 @@
+{
+  "name": "opencode-spec-driven-boilerplate",
+  "version": "0.1.0",
+  "description": "Spec-driven development boilerplate for opencode",
+  "type": "module",
+  "scripts": {
+    "prepare": "husky",
+    "build": "tsc",
+    "dev": "tsc --watch",
+    "lint": "eslint .",
+    "format": "npx prettier --write .",
+    "typecheck": "tsc --noEmit",
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "test:coverage": "vitest run --coverage",
+    "test:ui": "vitest --ui"
+  },
+  "keywords": [
+    "spec-driven-development",
+    "opencode",
+    "template"
+  ],
+  "author": "",
+  "license": "MIT",
+  "devDependencies": {
+    "@types/node": "^20.11.0",
+    "@vitest/coverage-v8": "^2.0.0",
+    "@vitest/ui": "^2.0.0",
+    "eslint": "^9.0.0",
+    "eslint-config-prettier": "^9.1.0",
+    "husky": "^9.0.0",
+    "lint-staged": "^15.2.0",
+    "prettier": "^3.2.0",
+    "typescript": "~5.3.0",
+    "typescript-eslint": "^8.0.0",
+    "vitest": "^2.0.0"
+  },
+  "lint-staged": {
+    "*.{ts,tsx}": [
+      "eslint --fix",
+      "prettier --write"
+    ]
+  }
+}