use pnpm for Desktop Electron App (#7679)

.github/copilot-instructions.md

@@ -60,17 +60,17 @@
 - `just check-openapi-schema` - OpenAPI schema validation
 
 **Desktop app checks:**
-- `npm ci` - Fresh dependency install (in `ui/desktop/`)
-- `npm run lint:check` - ESLint + Prettier
-- `npm run test:run` - Vitest tests
+- `pnpm install --frozen-lockfile` - Fresh dependency install (in `ui/desktop/`)
+- `pnpm run lint:check` - ESLint + Prettier
+- `pnpm run test:run` - Vitest tests
 
 **Setup steps CI performs:**
 - Installs system dependencies (libdbus, gnome-keyring, libxcb)
 - Activates hermit environment (`source bin/activate-hermit`)
-- Caches Cargo and npm dependencies
-- Runs `npm ci` before any npm scripts (ensures all packages are installed)
+- Caches Cargo and pnpm dependencies
+- Runs `pnpm install --frozen-lockfile` before any pnpm scripts (ensures all packages are installed)
 
-**Key insight**: Commands like `npx` check local `node_modules` first, which CI installs via `npm ci`. Don't flag these as broken unless you can explain why CI setup wouldn't handle it.
+**Key insight**: Commands like `npx` check local `node_modules` first, which CI installs via `pnpm install --frozen-lockfile`. Don't flag these as broken unless you can explain why CI setup wouldn't handle it.
 
 ## Skip These (Low Value)
 
@@ -78,7 +78,7 @@ Do not comment on:
 - **Style/formatting** - CI handles this (rustfmt, prettier)
 - **Clippy warnings** - CI handles this (clippy)
 - **Test failures** - CI handles this (full test suite)
-- **Missing dependencies** - CI handles this (npm ci will fail)
+- **Missing dependencies** - CI handles this (pnpm install will fail)
 - **Minor naming suggestions** - unless truly confusing
 - **Suggestions to add comments** - for self-documenting code
 - **Refactoring suggestions** - unless there's a clear bug or maintainability issue