Fix Playwright report comments on forked PRs (#1975)

## Summary
- update the Playwright summary script to support workflow_run events
and optional comment skipping
- stop the CI workflow from posting Playwright comments directly and
only generate the summary
- add a workflow_run-based commenter workflow that downloads artifacts
and posts results for PRs, including forks

## Testing
- not run (workflow changes only)


------
[Codex
Task](https://chatgpt.com/codex/tasks/task_e_694340b2da6083278e42db076ea89eba)

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Moves Playwright commenting to a workflow_run job that downloads
artifacts and posts/updates the summary; CI now only uploads the report,
and the summary script improves PR/run detection and OS bucketing.
> 
> - **Workflows**:
> - **CI (`.github/workflows/ci.yml`)**: Remove in-job PR comment step;
keep merging reports and uploading `playwright-report` artifact.
> - **New (`.github/workflows/playwright-comment.yml`)**: `workflow_run`
on CI to download artifacts (`html-report--attempt-*`, `blob-report-*`)
and run `scripts/generate-playwright-summary.js` to comment on the PR
(supports forks).
> - **Script (`scripts/generate-playwright-summary.js`)**:
> - Add PR detection for `workflow_run` and `PR_NUMBER`; use
`PLAYWRIGHT_RUN_ID` for report link.
> - Improve OS detection/bucketing (auto-detect from attachments/stacks,
sensible defaults, lazy bucket creation).
> - Safer fallbacks when no artifacts; always write job summary; skip PR
comment when no PR is detected.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
8428f7ad6eb0671571cb4ae0e473434ffb1cf8d1. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->



<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Fixes Playwright report comments on forked PRs by moving comment posting
to a workflow_run job. CI now only uploads the reports; a separate
workflow posts or updates the PR comment using artifacts.

- **Bug Fixes**
- Added Playwright Report Comment workflow (workflow_run on CI) to
download artifacts and comment on PRs from forks.
  - Removed PR comment step from CI; CI only uploads Playwright reports.
- Updated summary script to support workflow_run, auto-detect the PR
number, use PLAYWRIGHT_RUN_ID for links, and improve OS
detection/bucketing.

<sup>Written for commit 8428f7ad6eb0671571cb4ae0e473434ffb1cf8d1.
Summary will update automatically on new commits.</sup>

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

.github/workflows/ci.yml

@@ -151,10 +151,3 @@ jobs:
           name: html-report--attempt-${{ github.run_attempt }}
           path: playwright-report
           retention-days: 3
-
-      - name: Generate test summary comment
-        uses: actions/github-script@v7
-        with:
-          script: |
-            const { run } = require('./scripts/generate-playwright-summary.js');
-            await run({ github, context, core });