The Forgejo workflow_runs API has no head_branch field. For pull_request
events the branch lives in event_payload["pull_request"]["head"]["ref"];
for push events it is in prettyref. The old code used run.get("head_branch")
which always returned None, causing _latest_ci_run_for_branch to never find
the run and the loop to declare "no CI run after 15 min" and set the issue to
State/Question — even when CI had already passed.
Also fixes a pre-existing test mock that was missing the session_name kwarg.
Adds TestLatestCiRunForBranch covering both event types and the regression.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
