feat(desktop): Add recently opened workspaces service

[dang-hai]

Summary

• Add a service to track recently opened workspaces, helping users quickly reopen previously used workspaces
• WorkspaceSelectionModal now displays recent workspaces at the top for quick access
• Implements clean separation of concerns: modal is pure presentation, container handles business logic

Changes

• Database layer: Add recent_workspaces SQLite table with LRU eviction (max 20)
• IPC bridge: Expose recentWorkspaceAPI for main ↔ renderer communication
• Hook: Create useRecentWorkspaces for data fetching and state management
• View: Update WorkspaceSelectionModal as pure presentation (receives data via props)
• Container: AgentNode coordinates business logic and passes data to modal
• Styling: VS Code-style recent workspaces list with git branch display

Architecture

AgentNode (container)
    ↓ uses useRecentWorkspaces hook
    ↓ passes recentWorkspaces + callbacks as props
WorkspaceSelectionModal (view)
    ↓ user selects workspace
    ↓ calls onSelect(path)
AgentNode.handleWorkspaceSelect
    ↓ calls trackWorkspace (from hook)
    ↓ updates node attachments

Test plan

• Open desktop app with npm run dev:desktop
• Create an AgentNode and select a workspace
• Close and reopen the workspace selection modal - verify recent workspace appears
• Select multiple workspaces - verify LRU ordering (most recent first)
• Verify git branch is displayed for git repositories

🤖 Generated with Claude Code