feat(ProcessManager): add Bun availability check and improve PID file validation

- Implemented a method to check if Bun is available in the system PATH.
- Updated the startWithBun method to return an error if Bun is not found.
- Enhanced PID file parsing to validate required fields and their types.
- Cleaned up stale PID files if the process is no longer alive.

fix(SettingsRoutes): clear port cache after updating settings

- Added a call to clearPortCache after writing updated settings to ensure the application uses the latest configuration.

docs/public/architecture/overview.mdx

@@ -29,7 +29,7 @@ Claude-Mem operates as a Claude Code plugin with five core components:
 | **UI Framework**       | React + TypeScript                        |
 | **AI SDK**             | @anthropic-ai/claude-agent-sdk            |
 | **Build Tool**         | esbuild (bundles TypeScript)              |
-| **Process Manager**    | PM2                                       |
+| **Process Manager**    | Bun                                       |
 | **Testing**            | Node.js built-in test runner              |
 
 ## Data Flow
@@ -70,7 +70,7 @@ User Query → mem-search Skill Invoked → HTTP API → SessionSearch Service
                               ↓
 ┌─────────────────────────────────────────────────────────────────┐
 │ 1. Session Starts → Context Hook Fires                          │
-│    Starts PM2 worker if needed, injects context from previous   │
+│    Starts Bun worker if needed, injects context from previous   │
 │    sessions (configurable observation count)                    │
 └─────────────────────────────────────────────────────────────────┘
                               ↓
@@ -177,13 +177,13 @@ claude-mem/
 │
 ├── tests/                      # Test suite
 ├── docs/                       # Documentation
-└── ecosystem.config.cjs        # PM2 configuration
+└── ecosystem.config.cjs        # Process configuration (deprecated)
 ```
 
 ## Component Details
 
 ### 1. Plugin Hooks (6 Hooks)
-- **context-hook.js** - SessionStart: Starts PM2 worker, injects context
+- **context-hook.js** - SessionStart: Starts Bun worker, injects context
 - **user-message-hook.js** - UserMessage: Debugging hook
 - **new-hook.js** - UserPromptSubmit: Creates session, saves prompt
 - **save-hook.js** - PostToolUse: Captures tool executions
@@ -200,7 +200,7 @@ Express.js HTTP server on port 37777 (configurable) with:
 - 8 viewer UI HTTP/SSE endpoints
 - Async observation processing via Claude Agent SDK
 - Real-time updates via Server-Sent Events
-- Auto-managed by PM2 process manager
+- Auto-managed by Bun
 
 See [Worker Service](/architecture/worker-service) for HTTP API and endpoints.