feat: comment benchmark APK link on open PRs

Add PR commenting to the build-benchmark-apk workflow. When a build
completes, it now finds any open PR for the branch and posts a comment
with a direct download link to the benchmark APK artifact.

https://claude.ai/code/session_0138kUcZaPQoQcAc7nA1KDbf

.github/workflows/build-benchmark-apk.yml

@@ -48,9 +48,30 @@ jobs:
         with:
           script: |
             const runUrl = `${context.serverUrl}/${context.repo.owner}/${context.repo.repo}/actions/runs/${context.runId}`;
+            const artifactUrl = `${context.serverUrl}/${context.repo.owner}/${context.repo.repo}/actions/runs/${context.runId}/artifacts/${{ steps.upload.outputs.artifact-id }}`;
+            const body = `📦 **Benchmark APK ready!**\n\nDownload: [Play Benchmark APK](${artifactUrl})\n\nOr view all artifacts in the [workflow run](${runUrl}#artifacts).`;
+
             await github.rest.repos.createCommitComment({
               owner: context.repo.owner,
               repo: context.repo.repo,
               commit_sha: context.sha,
-              body: `📦 **Benchmark APK ready!**\n\nDownload it from the [workflow run artifacts](${runUrl}#artifacts).`
+              body
             });
+
+            // Find open PRs for this branch and comment on them
+            const branch = context.ref.replace('refs/heads/', '');
+            const { data: prs } = await github.rest.pulls.list({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              head: `${context.repo.owner}:${branch}`,
+              state: 'open'
+            });
+
+            for (const pr of prs) {
+              await github.rest.issues.createComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: pr.number,
+                body
+              });
+            }