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/installation.mdx

@@ -16,7 +16,7 @@ Install Claude-Mem directly from the plugin marketplace:
 
 That's it! The plugin will automatically:
 - Download prebuilt binaries (no compilation needed)
-- Install all dependencies (including PM2 and SQLite binaries)
+- Install all dependencies (including SQLite binaries)
 - Configure hooks for session lifecycle management
 - Auto-start the worker service on first session
 
@@ -26,7 +26,7 @@ Start a new Claude Code session and you'll see context from previous sessions au
 
 - **Node.js**: 18.0.0 or higher
 - **Claude Code**: Latest version with plugin support
-- **PM2**: Process manager (bundled with plugin - no global install required)
+- **Bun**: JavaScript runtime and process manager (auto-installed if missing)
 - **SQLite 3**: For persistent storage (bundled)
 
 ## Advanced Installation