feat(ci): add /update-snapshots comment trigger for PRs

- Comment '/update-snapshots' on any PR to update E2E snapshots
- Adds rocket reaction to acknowledge the command
- Comments back with result (updated or no changes needed)
- Removes hardcoded branch trigger
- Keeps workflow_dispatch for manual runs

Author: ochafik

.github/workflows/update-snapshots.yml

@@ -7,23 +7,50 @@ on:
         description: "Branch to update snapshots on"
         required: true
         default: "main"
-  # Temporary: auto-run on this branch to update snapshots
-  push:
-    branches:
-      - "ochafik/fix-e2e-flaky-tests"
-    paths:
-      - ".github/workflows/update-snapshots.yml"
+  issue_comment:
+    types: [created]
 
 permissions:
   contents: write
+  pull-requests: write
 
 jobs:
   update-snapshots:
+    # Run on workflow_dispatch OR when someone comments "/update-snapshots" on a PR
+    if: >
+      github.event_name == 'workflow_dispatch' ||
+      (github.event.issue.pull_request && contains(github.event.comment.body, '/update-snapshots'))
     runs-on: ubuntu-latest
     steps:
+      - name: Get PR branch
+        if: github.event_name == 'issue_comment'
+        id: pr
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const pr = await github.rest.pulls.get({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              pull_number: context.issue.number
+            });
+            core.setOutput('ref', pr.data.head.ref);
+            core.setOutput('sha', pr.data.head.sha);
+
+      - name: Add reaction to comment
+        if: github.event_name == 'issue_comment'
+        uses: actions/github-script@v7
+        with:
+          script: |
+            await github.rest.reactions.createForIssueComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              comment_id: context.payload.comment.id,
+              content: 'rocket'
+            });
+
       - uses: actions/checkout@v4
         with:
-          ref: ${{ github.event.inputs.branch || github.ref }}
+          ref: ${{ github.event.inputs.branch || steps.pr.outputs.ref || github.ref }}
           token: ${{ secrets.GITHUB_TOKEN }}
 
       - uses: oven-sh/setup-bun@v2
@@ -45,9 +72,32 @@ jobs:
         run: npx playwright test --update-snapshots --reporter=list
 
       - name: Commit updated snapshots
+        id: commit
         run: |
           git config user.name "github-actions[bot]"
           git config user.email "github-actions[bot]@users.noreply.github.com"
           git add tests/e2e/**/*.png
-          git diff --staged --quiet || git commit -m "chore: update e2e snapshots [skip ci]"
-          git push
+          if git diff --staged --quiet; then
+            echo "changed=false" >> $GITHUB_OUTPUT
+            echo "No snapshot changes to commit"
+          else
+            git commit -m "chore: update e2e snapshots [skip ci]"
+            git push
+            echo "changed=true" >> $GITHUB_OUTPUT
+          fi
+
+      - name: Comment on PR
+        if: github.event_name == 'issue_comment'
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const changed = '${{ steps.commit.outputs.changed }}' === 'true';
+            const body = changed
+              ? '✅ Snapshots updated and pushed to this branch.'
+              : '✅ No snapshot changes needed - all snapshots are up to date.';
+            await github.rest.issues.createComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.issue.number,
+              body
+            });