add /cc-ci-cleanup — reconcile, close dead PRs, report what actually blocks the rest

25 open recipe PRs had accumulated, and the list had stopped being readable: CI
sweep artifacts that were never meant to merge sat next to genuine CVE fixes, and
three PRs the operator had been told were outstanding were in fact already merged
upstream (discourse #6 with 140 CVEs, keycloak #6 with 12, n8n #5) — visible only
once the mirrors were reconciled.

The skill: reconcile every mirror from true upstream FIRST (that step alone closed
those three), survey every open PR deterministically, close the ones that cannot
merge or were never meant to, and report prioritised action items — CVE-carrying
first — for the ones that should land. It never merges a recipe PR.

pr-survey.py gathers the facts and decides nothing: behind_main, mergeable,
diff_files, which images the PR adds vs which are already pinned in main, the
newest !testme verdict, branch kind, age.

One correctness detail worth the extra state: a FAILED diff fetch is reported as
unknown, never as an empty diff. gitea #4 reads that way (force-pushed branch)
while being a verified green fix, and 'empty diff' is a close signal — so the
tool says DIFF-UNREADABLE(do not close on this) instead.

.opencode/skills/help/SKILL.md

@@ -31,6 +31,12 @@ Then present the roster grouped as follows, and close with the situation guide.
   PR). `--with-tests` also fixes that recipe's stale test.
 - **/recipe-report** — (re)generate the weekly report page for report.ci.commoninternet.net.
 
+**Keeping the PR list honest**
+- **/cc-ci-cleanup** — reconciles every mirror from true upstream (which alone closes PRs upstream
+  already merged), then closes the open recipe PRs that can no longer merge or were never meant to
+  (CI sweep artifacts, obsolete bumps, superseded duplicates) and reports what is actually blocking
+  the ones that should land. Never merges.
+
 **Security (CVEs)**
 - **/cve-check** — fleet-wide CVE sweep with **no upgrading**: for every recipe, work out what
   upgrade is available (per image, sidecars included), scan it for CVEs, and publish a CVE report.
@@ -81,6 +87,7 @@ ARM skills never touch cc-ci infra. After a submodule bump run `scripts/gen-ccte
 | "Run the weekly upgrades now" | `/upgrade-all` (or `systemctl start cc-ci-upgrade-all.service`) |
 | "Upgrade just <recipe>" | `/recipe-upgrade <recipe>` |
 | "The report site is stale/missing a week" | `/recipe-report` |
+| "The open PR list is a mess / what should I merge?" | `/cc-ci-cleanup` |
 | "What CVEs are we exposed to right now?" | `/cve-check` (read-only, no PRs) |
 | "A CVE just dropped — check and patch it" | `/cve-check-and-upgrade` (add `--min-severity high` to skip the noise) |
 | "Is <recipe> vulnerable?" | `/cve-check <recipe>` |