test(e2e): isolate fixed-port browser tab tests

[jackwener]

Summary

• move browser-tabs E2E into a dedicated e2e-fixed-port Vitest project that runs before the normal E2E group
• keep the rest of headed E2E parallel so the release gate does not slow down unnecessarily
• have browser-tabs shut down any stale OpenCLI daemon before binding the fixed bridge port 19825

Verification

• npx vitest run --project e2e-fixed-port tests/e2e/browser-tabs.test.ts --reporter=verbose
• npx vitest run tests/e2e/browser-tabs.test.ts tests/e2e/article-download-pipeline.test.ts --reporter=verbose
• npm run typecheck
• npm run build