## Summary
- Skip the Electron singleton lock for E2E test builds to allow multiple
app instances to run concurrently
- Update Playwright config to use 2 workers for parallel test execution

## Performance Impact
With parallelism of 2, tests should complete approximately **~1.6-1.8x
faster** (not a perfect 2x due to overhead and some sequential test
dependencies). The speedup comes from:
- Two Electron app instances can now run simultaneously during E2E tests
- Previously, the singleton lock (`app.requestSingleInstanceLock()`)
would cause second instances to quit immediately

## Implementation Details
- Modified `src/main.ts` to check `IS_TEST_BUILD` and skip the singleton
lock for e2e test builds
- Changed `playwright.config.ts` from `workers: 1` to `workers: 2`

## Test plan
- [ ] Run `npm run build` to ensure the e2e build compiles correctly
- [ ] Run `npx playwright test` to verify tests pass with parallel
execution
- [ ] Verify no race conditions occur when multiple app instances run
simultaneously

🤖 Generated with [Claude Code](https://claude.com/claude-code)
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<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Enable parallel Playwright E2E tests by skipping Electron’s
single-instance lock in test builds and reading worker count from
PLAYWRIGHT_PARALLELISM. CI sets 3 workers on self-hosted macOS (1
elsewhere), keeping single-instance behavior in production.

- **Bug Fixes**
- Prevent crash in second-instance handler when no deep link URL;
clarify deep link handling for test builds.

<sup>Written for commit 0f542e189f5b17cc857acc9ad07955c47a0049f1.
Summary will update on new commits.</sup>

<!-- End of auto-generated description by cubic. -->

---------
Co-authored-by: Will Chen <willchen90@gmail.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>