ci: gate rio-v2 full-suite jobs on schedule; document lifecycle

.github/workflows/cache-warm.yml

@@ -182,7 +182,12 @@ jobs:
             echo '```'
           } >> "$GITHUB_STEP_SUMMARY"
 
-  # Readers: test-and-lint-rio-v2, build-rustfs-debug-binary-rio-v2.
+  # Readers: test-and-lint-rio-v2 (per-PR), build-rustfs-debug-binary-rio-v2
+  # (weekly schedule / manual dispatch only — dormant rio-v2 variant, see
+  # rustfs/backlog#1835 and docs/architecture/minio-file-format-compat.md).
+  # The second build below stays despite the reduced cadence: it warms the
+  # rio-v2,e2e-test-hooks feature resolution the scheduled build restores,
+  # which keeps that lane inside its 30-minute timeout.
   warm-ci-feat-rio:
     name: Warm ci-feat-rio
     runs-on: sm-standard-4

.github/workflows/ci.yml

@@ -533,7 +533,12 @@ jobs:
 
   build-rustfs-debug-binary-rio-v2:
     name: Build RustFS Debug Binary (rio-v2)
-    if: github.event_name != 'pull_request' || github.event.action != 'closed'
+    # Dormant rio-v2 variant (rustfs/backlog#1835): the feature ships in no
+    # default build, so this full-suite lane runs only on the weekly schedule
+    # and manual dispatch. Per-PR cfg-seam coverage stays with
+    # test-and-lint-rio-v2. Lifecycle and the promote-or-delete condition:
+    # docs/architecture/minio-file-format-compat.md ("rio-v2 variant lifecycle").
+    if: github.event_name == 'schedule' || github.event_name == 'workflow_dispatch'
     needs: [ quick-checks ]
     runs-on: sm-standard-4
     timeout-minutes: 30
@@ -824,6 +829,9 @@ jobs:
 
   e2e-tests-rio-v2:
     name: End-to-End Tests (rio-v2)
+    # Inherits the schedule/dispatch-only gate through needs: on every other
+    # event build-rustfs-debug-binary-rio-v2 is skipped, so this job skips
+    # with it (see the dormant-variant comment on that job).
     needs: [ build-rustfs-debug-binary-rio-v2 ]
     runs-on: sm-standard-2
     timeout-minutes: 30