refactor: extract shared resolve-pr-from-workflow-run action (#11336)

## Summary

Extract duplicated PR-number-resolution logic from
`workflow_run`-triggered workflows into a shared composite action at
`.github/actions/resolve-pr-from-workflow-run/`.

## Changes

- **What**: New composite action that resolves PR number from
`workflow_run` context using `pull_requests[0]` with
`listPullRequestsAssociatedWithCommit` fallback. Updated 4 consumer
workflows; removed dead artifact-stored PR metadata from 2 CI workflows.
- **Files touched**:
  - `.github/actions/resolve-pr-from-workflow-run/action.yaml` (new)
- `.github/workflows/pr-vercel-website-preview.yaml` (uses shared
action)
- `.github/workflows/pr-report.yaml` (uses shared action with
`check-staleness: true`)
- `.github/workflows/ci-tests-storybook-forks.yaml` (replaced
`pulls.list` scan)
- `.github/workflows/ci-tests-e2e-forks.yaml` (replaced `pulls.list`
scan)
- `.github/workflows/ci-size-data.yaml` (removed dead
`number.txt`/`base.txt`/`head-sha.txt` writes)
- `.github/workflows/ci-perf-report.yaml` (removed dead `perf-meta`
artifact)

## Review Focus

- The fork workflows previously used `pulls.list` (fetches all open PRs,
linear scan by SHA). The shared action uses the more targeted
`workflow_run.pull_requests[0]` + `listPullRequestsAssociatedWithCommit`
fallback.
- `coverage-slack-notify.yaml` was intentionally left unchanged — it
parses merged commit messages on `main` pushes, which is a different use
case.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-11336-refactor-extract-shared-resolve-pr-from-workflow-run-action-3456d73d365081e5b8f5ea29c020763e)
by [Unito](https://www.unito.io)

---------

Co-authored-by: bymyself <cbyrne@comfy.org>
Co-authored-by: Amp <amp@ampcode.com>

.github/workflows/pr-report.yaml

@@ -30,42 +30,7 @@ jobs:
 
       - name: Resolve PR from workflow_run context
         id: pr-meta
-        uses: actions/github-script@v8
-        with:
-          script: |
-            let pr = context.payload.workflow_run.pull_requests?.[0];
-            if (!pr) {
-              const { data: prs } = await github.rest.repos.listPullRequestsAssociatedWithCommit({
-                owner: context.repo.owner,
-                repo: context.repo.repo,
-                commit_sha: context.payload.workflow_run.head_sha,
-              });
-              pr = prs.find(p => p.state === 'open');
-            }
-
-            if (!pr) {
-              core.info('No open PR found for this workflow run — skipping.');
-              core.setOutput('skip', 'true');
-              return;
-            }
-
-            // Verify the workflow_run head SHA matches the current PR head
-            const { data: livePr } = await github.rest.pulls.get({
-              owner: context.repo.owner,
-              repo: context.repo.repo,
-              pull_number: pr.number,
-            });
-
-            if (livePr.head.sha !== context.payload.workflow_run.head_sha) {
-              core.info(`Stale run: workflow SHA ${context.payload.workflow_run.head_sha} != PR head ${livePr.head.sha}`);
-              core.setOutput('skip', 'true');
-              return;
-            }
-
-            core.setOutput('skip', 'false');
-            core.setOutput('number', String(pr.number));
-            core.setOutput('base', livePr.base.ref);
-            core.setOutput('head-sha', livePr.head.sha);
+        uses: ./.github/actions/resolve-pr-from-workflow-run
 
       - name: Find size workflow run
         if: steps.pr-meta.outputs.skip != 'true'