feat(FN-1073): add desktop CLI workflow and packaging support

- 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

packages/cli/vitest.config.ts

@@ -6,7 +6,9 @@ export default defineConfig({
   test: {
     include: ["src/**/*.test.ts"],
     maxWorkers,
-    fileParallelism: true,
+    // build-exe and build-exe-cross suites both operate on packages/cli/dist/
+    // and can race when run in parallel workers.
+    fileParallelism: false,
     coverage: {
       enabled: false,
       reporter: ["text", "html", "json"],