feat: add webcam source selector with stable HUD layout

- Add useCameraDevices hook to enumerate video input devices
- Update useScreenRecorder to support webcamDeviceId selection
- Add device selector UI above HUD bar (mic + webcam, hover-to-expand)
- All selectors and HUD bar are absolute-positioned to prevent layout shifts
- Increase HUD window to 600x200px to accommodate device panels
- Add unit tests for useCameraDevices hook

package.json

@@ -70,6 +70,9 @@
 	"devDependencies": {
 		"@biomejs/biome": "^2.3.13",
 		"@playwright/test": "^1.58.2",
+		"@testing-library/jest-dom": "^6.9.1",
+		"@testing-library/react": "^16.3.2",
+		"@testing-library/user-event": "^14.6.1",
 		"@types/node": "^25.0.3",
 		"@types/react": "^18.2.64",
 		"@types/react-dom": "^18.2.21",
@@ -82,6 +85,7 @@
 		"electron-rebuild": "^3.2.9",
 		"fast-check": "^4.5.2",
 		"husky": "^9.1.7",
+		"jsdom": "^29.0.1",
 		"lint-staged": "^16.3.2",
 		"postcss": "^8.5.6",
 		"tailwindcss": "^3.4.18",