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/playwright-comment.yml

@@ -0,0 +1,59 @@
+name: Playwright Report Comment
+
+on:
+  workflow_run:
+    workflows: ["CI"]
+    types:
+      - completed
+
+permissions:
+  contents: read
+  pull-requests: write
+  issues: write
+  actions: read
+
+jobs:
+  comment:
+    if: ${{ github.event.workflow_run.event == 'pull_request' && github.event.workflow_run.pull_requests[0].number }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.workflow_run.base_ref }}
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: lts/*
+
+      - name: Download Playwright HTML report
+        uses: actions/download-artifact@v4
+        with:
+          name: html-report--attempt-${{ github.event.workflow_run.run_attempt }}
+          path: playwright-report
+          github-token: ${{ github.token }}
+          repository: ${{ github.event.workflow_run.repository.full_name }}
+          run-id: ${{ github.event.workflow_run.id }}
+          if-no-artifact-found: warn
+
+      - name: Download blob reports
+        uses: actions/download-artifact@v4
+        with:
+          path: all-blob-reports
+          pattern: blob-report-*
+          merge-multiple: true
+          github-token: ${{ github.token }}
+          repository: ${{ github.event.workflow_run.repository.full_name }}
+          run-id: ${{ github.event.workflow_run.id }}
+          if-no-artifact-found: warn
+
+      - name: Generate Playwright summary comment
+        uses: actions/github-script@v7
+        env:
+          PR_NUMBER: ${{ github.event.workflow_run.pull_requests[0].number }}
+          PLAYWRIGHT_RUN_ID: ${{ github.event.workflow_run.id }}
+        with:
+          script: |
+            const { run } = require('./scripts/generate-playwright-summary.js');
+            await run({ github, context, core });