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/tools/AGENTS.md

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+# TOOLS KNOWLEDGE BASE
+
+## OVERVIEW
+
+Custom tools extending agent capabilities: LSP integration (11 tools), AST-aware code search/replace, file operations with timeouts, background task management.
+
+## STRUCTURE
+
+```
+tools/
+├── ast-grep/           # AST-aware code search/replace (25 languages)
+│   ├── cli.ts          # @ast-grep/cli subprocess
+│   ├── napi.ts         # @ast-grep/napi native binding (preferred)
+│   ├── constants.ts, types.ts, tools.ts, utils.ts
+├── background-task/    # Async agent task management
+├── call-omo-agent/     # Spawn explore/librarian agents
+├── glob/               # File pattern matching (timeout-safe)
+├── grep/               # Content search (timeout-safe)
+├── interactive-bash/   # Tmux session management
+├── look-at/            # Multimodal analysis (PDF, images)
+├── lsp/                # 11 LSP tools
+│   ├── client.ts       # LSP connection lifecycle
+│   ├── config.ts       # Server configurations
+│   ├── tools.ts        # Tool implementations
+│   └── types.ts
+├── slashcommand/       # Slash command execution
+└── index.ts            # builtinTools export
+```
+
+## TOOL CATEGORIES
+
+| Category | Tools | Purpose |
+|----------|-------|---------|
+| LSP | lsp_hover, lsp_goto_definition, lsp_find_references, lsp_document_symbols, lsp_workspace_symbols, lsp_diagnostics, lsp_servers, lsp_prepare_rename, lsp_rename, lsp_code_actions, lsp_code_action_resolve | IDE-like code intelligence |
+| AST | ast_grep_search, ast_grep_replace | Pattern-based code search/replace |
+| File Search | grep, glob | Content and file pattern matching |
+| Background | background_task, background_output, background_cancel | Async agent orchestration |
+| Multimodal | look_at | PDF/image analysis via Gemini |
+| Terminal | interactive_bash | Tmux session control |
+| Commands | slashcommand | Execute slash commands |
+| Agents | call_omo_agent | Spawn explore/librarian |
+
+## HOW TO ADD A TOOL
+
+1. Create directory: `src/tools/my-tool/`
+2. Create files:
+   - `constants.ts`: `TOOL_NAME`, `TOOL_DESCRIPTION`
+   - `types.ts`: Parameter/result interfaces
+   - `tools.ts`: Tool implementation (returns OpenCode tool object)
+   - `index.ts`: Barrel export
+   - `utils.ts`: Helpers (optional)
+3. Add to `builtinTools` in `src/tools/index.ts`
+
+## LSP SPECIFICS
+
+- **Client lifecycle**: Lazy init on first use, auto-shutdown on idle
+- **Config priority**: opencode.json > oh-my-opencode.json > defaults
+- **Supported servers**: typescript-language-server, pylsp, gopls, rust-analyzer, etc.
+- **Custom servers**: Add via `lsp` config in oh-my-opencode.json
+
+## AST-GREP SPECIFICS
+
+- **Meta-variables**: `$VAR` (single node), `$$$` (multiple nodes)
+- **Languages**: 25 supported (typescript, tsx, python, rust, go, etc.)
+- **Binding**: Prefers @ast-grep/napi (native), falls back to @ast-grep/cli
+- **Pattern must be valid AST**: `export async function $NAME($$$) { $$$ }` not fragments
+
+## ANTI-PATTERNS (TOOLS)
+
+- **No timeout**: Always use timeout for file operations (default 60s)
+- **Blocking main thread**: Use async/await, never sync file ops
+- **Ignoring LSP errors**: Gracefully handle server not found/crashed
+- **Raw subprocess for ast-grep**: Prefer napi binding for performance