docs: add hierarchical AGENTS.md for hooks, tools, features

Create directory-specific knowledge bases for high-complexity directories:
- src/hooks/AGENTS.md: Documents 21 hooks across 86 files
- src/tools/AGENTS.md: Documents 11 LSP tools, AST-Grep, MCP, background tasks (50 files)
- src/features/AGENTS.md: Documents 6 Claude Code compatibility features (24 files)

Root AGENTS.md updated to reference these specialized guides while maintaining project overview. Enables better navigation and reduces cognitive load for developers working in specific areas.

🤖 Generated with assistance of OhMyOpenCode (https://github.com/code-yeongyu/oh-my-opencode)

src/features/AGENTS.md

@@ -0,0 +1,78 @@
+# FEATURES KNOWLEDGE BASE
+
+## OVERVIEW
+
+Claude Code compatibility layer and core feature modules. Enables Claude Code configs/commands/skills/MCPs/hooks to work seamlessly in OpenCode.
+
+## STRUCTURE
+
+```
+features/
+├── background-agent/           # Background task management
+│   ├── manager.ts              # Task lifecycle, notifications
+│   ├── manager.test.ts
+│   └── types.ts
+├── claude-code-agent-loader/   # Load agents from ~/.claude/agents/*.md
+├── claude-code-command-loader/ # Load commands from ~/.claude/commands/*.md
+├── claude-code-mcp-loader/     # Load MCPs from .mcp.json
+│   └── env-expander.ts         # ${VAR} expansion
+├── claude-code-session-state/  # Session state persistence
+├── claude-code-skill-loader/   # Load skills from ~/.claude/skills/*/SKILL.md
+└── hook-message-injector/      # Inject messages into conversation
+```
+
+## LOADER PRIORITY
+
+Each loader reads from multiple directories (highest priority first):
+
+| Loader | Priority Order |
+|--------|---------------|
+| Commands | `.opencode/command/` > `~/.config/opencode/command/` > `.claude/commands/` > `~/.claude/commands/` |
+| Skills | `.claude/skills/` > `~/.claude/skills/` |
+| Agents | `.claude/agents/` > `~/.claude/agents/` |
+| MCPs | `.claude/.mcp.json` > `.mcp.json` > `~/.claude/.mcp.json` |
+
+## HOW TO ADD A LOADER
+
+1. Create directory: `src/features/claude-code-my-loader/`
+2. Create files:
+   - `loader.ts`: Main loader logic with `load()` function
+   - `types.ts`: TypeScript interfaces
+   - `index.ts`: Barrel export
+3. Pattern: Read from multiple dirs, merge with priority, return normalized config
+
+## BACKGROUND AGENT SPECIFICS
+
+- **Task lifecycle**: pending → running → completed/failed
+- **Notifications**: OS notification on task complete (configurable)
+- **Result retrieval**: `background_output` tool with task_id
+- **Cancellation**: `background_cancel` with task_id or all=true
+
+## CONFIG TOGGLES
+
+Disable features in `oh-my-opencode.json`:
+
+```json
+{
+  "claude_code": {
+    "mcp": false,      // Skip .mcp.json loading
+    "commands": false, // Skip commands/*.md loading
+    "skills": false,   // Skip skills/*/SKILL.md loading
+    "agents": false,   // Skip agents/*.md loading
+    "hooks": false     // Skip settings.json hooks
+  }
+}
+```
+
+## HOOK MESSAGE INJECTOR
+
+- **Purpose**: Inject system messages into conversation at specific points
+- **Timing**: PreToolUse, PostToolUse, UserPromptSubmit, Stop
+- **Format**: Returns `{ messages: [{ role: "user", content: "..." }] }`
+
+## ANTI-PATTERNS (FEATURES)
+
+- **Blocking on load**: Loaders run at startup, keep them fast
+- **No error handling**: Always try/catch, log failures, return empty on error
+- **Ignoring priority**: Higher priority dirs must override lower
+- **Modifying user files**: Loaders read-only, never write to ~/.claude/