feat: redesign the desktop workspace

Add a compact top navigation, contextual sidebars, responsive workspaces, accessible theme cards, and a persistent updater control. Preserve all existing renderer IDs and actions while adding an isolated Electron UI contract across the supported desktop sizes.

package.json

@@ -15,6 +15,7 @@
     "test:e2e": "node scripts/smoke-test.js",
     "test:e2e:guide": "node scripts/smoke-test-template-guide.js",
     "test:e2e:full": "node scripts/smoke-test-full.js",
+    "test:e2e:workspace-ui": "npm run build && node scripts/smoke-test-workspace-ui.js",
     "test:e2e:release": "npm run build && npm run test:unit && npm run test:e2e:update-logic && npm run test:e2e:public-release && npm run test:e2e && npm run test:e2e:guide && npm run test:e2e:full",
     "test:e2e:stress": "npm run test:e2e:release && npm run test:e2e:release && npm run test:e2e:release",
     "pack": "npm run build && electron-builder --dir",
@@ -47,6 +48,7 @@
       "dist/**/*",
       "src/index.html",
       "src/styles.css",
+      "src/workspace.css",
       "package.json"
     ],
     "directories": {