Adds parameterized test cases to the worktree-liveness test to exercise different configured `worktreesDir` paths, improving coverage of the worktree escape/isolation path.
Fusion-Task-Id: FN-4737
Fusion-Task-Lineage: 40e262ea-2507-461e-b9f5-940b3b4490f9
- 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