[ci] Fix missing user name during manual workflow dispatch

It seems like the github.event.workflow_run payload is only populated
for non manual runs of the workflow, so this would crash the manual
dispatch. Instead, use the top level triggering_actor property

Test plan: https://github.com/facebook/react/actions/runs/11017512571
completes

ghstack-source-id: 90f24e048289d10d467302129bfe6c4c2a09ea20
Pull Request resolved: #31045

.github/workflows/runtime_commit_artifacts.yml

@@ -245,12 +245,12 @@ jobs:
         uses: stefanzweifel/git-auto-commit-action@v4
         with:
           commit_message: |
-            ${{ github.event.workflow_run.head_commit.message }}
+            ${{ github.event.workflow_run.head_commit.message || 'No commit message' }}
 
-            DiffTrain build for [${{ github.event.workflow_run.head_sha }}](https://github.com/facebook/react/commit/${{ github.event.workflow_run.head_sha }})
+            DiffTrain build for [${{ github.sha }}](https://github.com/facebook/react/commit/${{ github.sha }})
           branch: builds/facebook-www
-          commit_user_name: ${{ github.event.workflow_run.triggering_actor.login }}
-          commit_user_email: ${{ github.event.workflow_run.triggering_actor.email || format('{0}@users.noreply.github.com', github.event.workflow_run.triggering_actor.login) }}
+          commit_user_name: ${{ github.triggering_actor }}
+          commit_user_email: ${{ format('{0}@users.noreply.github.com', github.triggering_actor) }}
           create_branch: true
 
   commit_fbsource_artifacts:
@@ -412,10 +412,10 @@ jobs:
         uses: stefanzweifel/git-auto-commit-action@v4
         with:
           commit_message: |
-            ${{ github.event.workflow_run.head_commit.message }}
+            ${{ github.event.workflow_run.head_commit.message || 'No commit message' }}
 
-            DiffTrain build for commit https://github.com/facebook/react/commit/${{ github.event.workflow_run.head_sha }}.
+            DiffTrain build for commit https://github.com/facebook/react/commit/${{ github.sha }}.
           branch: builds/facebook-fbsource
-          commit_user_name: ${{ github.event.workflow_run.triggering_actor.login }}
-          commit_user_email: ${{ github.event.workflow_run.triggering_actor.email || format('{0}@users.noreply.github.com', github.event.workflow_run.triggering_actor.login) }}
+          commit_user_name: ${{ github.triggering_actor }}
+          commit_user_email: ${{ format('{0}@users.noreply.github.com', github.triggering_actor) }}
           create_branch: true