Adds a local runtime manager to the desktop app (FN-3404) — an embedded engine process managed via IPC with packaging for bundled dependencies and lifecycle documentation. Also includes project mapping onboarding UI with persistence and rollback (FN-3505), plus related dashboard API and hook updates
Fusion-Task-Id: FN-3404
- Add new `fn desktop` CLI command with argument handling and comprehensive command/bin tests
- Implement desktop build and hot-reload dev scripts and wire package scripts/dependencies for Electron workflows
- Add electron-builder configuration and desktop main-process/integration test coverage to stabilize packaging behavior
- Document desktop development and usage in README files and include a changeset for the published CLI package
- Add dedicated desktop tray and menu modules, including platform-aware menu templates and tray status/visibility controls
- Integrate tray setup, app menu initialization, and tray status exports into the Electron main process bootstrap
- Add tray icon assets plus an icon generation script and update desktop package dependencies/lockfile
- Expand desktop test coverage with new menu/tray test suites and main process integration assertions
- Update desktop README with tray and application menu usage/documentation
