fix(actions): correctness and hardening fixes (#38518)

Various fixes to actions

1. **Cap total jobs per run in reusable-workflow expansion** — only
nesting depth was capped, so fan-out + nested reusable workflows could
explode job-row inserts and exhaust the DB from a single push. Now
enforces `MaxJobNumPerRun` in the insert path.
2. **Reject rerun-failed when a run has no failed jobs** — an empty job
list meant "re-run everything", so `rerun-failed` on a green run re-ran
all jobs. Now errors (web + API).
3. **Don't adopt external commit statuses into the legacy hash** — the
pre-#35699 Context-only hash matched API-posted statuses too, collapsing
two same-named workflows into one check. Now limited to Actions-user
rows.
4. **Don't cut post-cancel cleanup short in `StopEndlessTasks`** — the
sweep force-stopped just-cancelled jobs mid-cleanup. Now targets
`StatusRunning` only; stalled cancels stay covered by `StopZombieTasks`.
5. **Avoid redundant run reload in `GenerateGiteaContext`** — resolving
`github.triggering_actor` reloaded the run already passed in. Now loads
only the trigger user via new `ActionRunAttempt.LoadTriggerUser`.

---------

Co-authored-by: Zettat123 <zettat123@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

options/locale/locale_en-US.json

@@ -3806,6 +3806,7 @@
   "actions.runs.cancel": "Cancel workflow run",
   "actions.runs.delete.description": "Are you sure you want to permanently delete this workflow run? This action cannot be undone.",
   "actions.runs.not_done": "This workflow run is not done.",
+  "actions.runs.no_failed_jobs": "This workflow run has no failed jobs to re-run.",
   "actions.runs.view_workflow_file": "View workflow file",
   "actions.runs.summary": "Summary",
   "actions.runs.all_jobs": "All jobs",