feat(#1778): add hive-forge ci-rerun to re-run CI without an empty commit

When a CI run fails for a transient reason (remote-builder flap, cold-daemon
window, act_runner hiccup) the only retrigger path was an empty commit, which
litters PR history and forces a force-push to clean up. This verb POSTs the
rerun action directly.

- `ci-rerun --run <n>` re-runs all jobs of a run (run number = the `runs/<n>`
  the UI shows, same value ci-log / artifact-get take, surfaced as a CI
  context's target_url by pr-status).
- `--pr <n>` resolves the run from the PR head sha's CI status target_url.
- `--job <i>` re-runs a single job.

Forgejo exposes no REST endpoint for rerunning a run, so this rides the run
page's web routes (`<base>/<owner>/<repo>/actions/runs/<n>[/jobs/<i>]/rerun`)
via a new `Client::post_web_no_content` (web base like post_json_web, tolerates
the redirect/empty response the rerun handler returns). Mirrors ci-log's
web-route approach + auth path.

docs/tools/forge.md updated with the verb.

hive-forge/src/verbs/mod.rs

@@ -9,6 +9,7 @@ pub mod attach;
 pub mod attachment_get;
 pub mod branches;
 pub mod ci_log;
+pub mod ci_rerun;
 pub mod clone;
 pub mod close;
 pub mod comment;