fix(5 A5-1/A5-2): bridge commit status posting + enroll custom-html-tiny

A5-2: bridge.py now posts Gitea commit statuses on the recipe PR's head SHA:
- pending on build trigger (so testme-on-pr.sh sees the run immediately)
- success/failure on build finish (so testme-on-pr.sh returns VERDICT=GREEN/RED)
Added post_commit_status() using the existing _api() helper + GITEA_TOKEN.
Called from process_testme() (pending) and watch_and_reflect() (terminal state).

A5-1: added recipe-maintainers/custom-html-tiny to bridge POLL_REPOS in
bridge.nix so !testme on custom-html-tiny PRs is picked up by the bridge poller.

machine-docs/STATUS-5.md

@@ -0,0 +1,32 @@
+# STATUS — cc-ci Phase 5 Builder
+
+**Phase:** 5 — Verify `/recipe-upgrade` + `testme-on-pr.sh` end-to-end flow
+**SSOT:** `/srv/cc-ci/cc-ci-plan/plan-phase5-verify-upgrade-flow.md`
+**Started:** 2026-05-31
+
+## Current focus
+
+Running V3 — `/recipe-upgrade custom-html-tiny` end-to-end (V1/V2/V7 evidence collected alongside).
+
+## Verification item status
+
+| Item | Status | Evidence |
+|---|---|---|
+| V1 — !testme trigger + result-back | IN PROGRESS | D1 PASS from Phase 3 (REVIEW.md); fresh run pending via V3 |
+| V2 — testme-on-pr.sh reads verdict | IN PROGRESS | Running via V3 flow |
+| V3 — /recipe-upgrade sandbox GREEN | IN PROGRESS | custom-html-tiny upgrade underway |
+| V4 — 3-iter regression loop | TODO | |
+| V5 — stale-test DEFAULT = comment | TODO | |
+| V6 — --with-tests opens+verifies cc-ci test PR | TODO | |
+| V7 — mirror reconciliation | IN PROGRESS | open-recipe-pr.sh reconciler running |
+| V8 — /upgrade-all DEFAULT run | TODO | |
+| V8a — cc-ci-upgrader agent | TODO | |
+| V9 — cleanup | TODO | |
+
+## Phase 5 gates
+
+(None claimed yet — working V3.)
+
+## Blocked
+
+(none)