Pin VS Code E2E tests to stable version and add job timeout

- Add --quality=stable to vscode-test-web to use stable VS Code instead of
  Insiders, which can break CI with untested changes
- Add timeout-minutes: 15 to E2E job to fail fast on hangs

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: charlespwd

.github/workflows/ci.yml

@@ -34,6 +34,7 @@ jobs:
   e2e:
     runs-on: ubuntu-latest
     name: E2E tests
+    timeout-minutes: 15
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
         with:

packages/vscode-extension/package.json

@@ -55,7 +55,7 @@
     "pretest:web": "[ -d .tmp/dawn ] || git clone --depth 1 https://github.com/Shopify/dawn.git .tmp/dawn",
     "build:test": "webpack --config webpack.test.config.js --mode development",
     "build:test:watch": "WATCH_MODE=1 webpack --config webpack.test.config.js --mode development --watch",
-    "test:web": "yarn build:test && vscode-test-web --headless --extensionDevelopmentPath=. --extensionTestsPath=./dist/browser/test/suite/index.js .tmp/dawn",
+    "test:web": "yarn build:test && vscode-test-web --quality=stable --headless --extensionDevelopmentPath=. --extensionTestsPath=./dist/browser/test/suite/index.js .tmp/dawn",
     "test:web:watch": "vscode-test-web --open-devtools --extensionDevelopmentPath=. --extensionTestsPath=./dist/browser/test/suite/index.js .tmp/dawn",
     "type-check:test": "tsc --project test/tsconfig.json --noEmit",
     "type-check": "tsc --noEmit"