feat(Cocoon): Implement sidecar process lifecycle management

Added process management handler to launch and initialize Cocoon Node.js extension host sidecar. Key aspects:
- Locates bundled Node.js runtime and Cocoon entry script using Tauri's PathResolver
- Spawns Cocoon process with stdio pipes for Vine IPC communication
- Implements ready signal handshake via `vine://sidecar/ready` event
- Constructs `IExtensionHostInitData` payload from AppState including:
  - Workspace configuration and folder URIs
  - Scanned extensions metadata and activation events
  - Effective configuration settings
  - Proposed API enablement status
  - Telemetry and environment paths
- Integrates with Vine IPC for notification delivery
- Implements stderr capture and process cleanup

Enables critical extension host initialization flow required for VS Code extension compatibility in Land's architecture. Establishes foundation for extension activation and RPC communication via Cocoon shim layer.

Author: NikolaRHristov