fix(ci): skip github.ref-gated jobs in ci_job_names (mc#958 mc#959)

Adds `github.ref` as a skip condition in ci_job_names(), matching the
existing github.event_name skip. Jobs gated on github.ref (e.g.
canvas-deploy-reminder: only runs on pushes to refs/heads/main) never
execute in a PR context, so flagging them as missing from
all-required.needs: is a false positive that triggers mc#958/mc#959.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.gitea/scripts/ci-required-drift.py

@@ -13,8 +13,9 @@ Sources:
 Three failure classes:
   F1  Job in (A) is not under the sentinel's `needs:` — sentinel
       doesn't gate it, so a red job on that name can sneak through.
-      Ignores jobs whose `if:` references `github.event_name` (those
-      run only on specific events and may be `skipped` legitimately).
+      Ignores jobs whose `if:` references `github.event_name` or
+      `github.ref` (those run only on specific events or refs and may
+      be `skipped` legitimately).
   F2  Context in (B) corresponds to no emitter — i.e. there's no job
       in ci.yml whose runtime status-name maps to that context.
       A stale required-check name is silent: protection demands a
@@ -203,12 +204,17 @@ def ci_jobs_all(ci_doc: dict) -> set[str]:
 
 def ci_job_names(ci_doc: dict) -> set[str]:
     """Set of job keys in ci.yml MINUS the sentinel itself MINUS jobs
-    whose `if:` gates on `github.event_name` (those are event-scoped
-    and can legitimately be `skipped` for a given trigger; if we
-    required them under the sentinel `needs:`, every PR-only job
+    whose `if:` gates on `github.event_name` or `github.ref` (those are
+    event-scoped and can legitimately be `skipped` for a given trigger;
+    if we required them under the sentinel `needs:`, every PR-only job
     would be `skipped` on push and the sentinel would interpret
     `skipped != success` as failure). RFC §4 spec.
 
+    `github.ref` is the companion gate for jobs that run only on direct
+    pushes to specific branches (e.g. `github.ref == 'refs/heads/main'`).
+    These never execute in a PR context, so flagging them as missing
+    from `all-required.needs:` is a false positive (mc#958 / mc#959).
+
     Used for F1 (jobs missing from sentinel needs). NOT used for F1b
     (typos in needs) — see `ci_jobs_all` for that."""
     jobs = ci_doc.get("jobs")
@@ -221,7 +227,9 @@ def ci_job_names(ci_doc: dict) -> set[str]:
             continue
         if isinstance(v, dict):
             gate = v.get("if")
-            if isinstance(gate, str) and "github.event_name" in gate:
+            if isinstance(gate, str) and (
+                "github.event_name" in gate or "github.ref" in gate
+            ):
                 continue
         names.add(k)
     return names