build(desktop): wire the Electron app into the workspace and build graph

Add desktop:dev/build/pack scripts, approve the electron build script in
pnpm-workspace.yaml allowBuilds, and reference apps/desktop (plus its
tests) in the host TypeScript program. Records the electron and
electron-builder deps in the lockfile.

Co-Authored-By: Claude <noreply@anthropic.com>

tsconfig.host.json

@@ -83,6 +83,7 @@
     "apps/web/tests/workflow-run.e2e.ts",
     "apps/web/stress-tests/reasoning-chunks.stress.ts",
     "apps/cli/tests/**/*.ts",
+    "apps/desktop/tests/**/*.ts",
     "examples/*/src/**/*.ts",
     "examples/*/start.ts",
     "examples/*/tests/**/*.ts",
@@ -293,6 +294,7 @@
     { "path": "./packages/lsp/lsp" },
     { "path": "./packages/lsp/lsp-stdio" },
     { "path": "./packages/lsp/tool-lsp" },
-    { "path": "./apps/cli" }
+    { "path": "./apps/cli" },
+    { "path": "./apps/desktop" }
   ]
 }