fix(ci): gate the three ungated pipelines on their own variable

A manual pipeline creation instantiates every pipeline in .crow/, so one whose
only manual condition is a bare `event: manual` fires on any manual trigger in
this repo. auto-apply-patches, weekly-patch-proposals and trial-build-registry
were in that state and all ran unintentionally alongside a manual
process-updates run.

- gate each on a variable named after the pipeline, defaulting to 'false', as
  repair-built-stamp.yaml documents and the other pipelines already do
- refresh the stale run-manually comments, which still referenced a `task`
  variable that no pipeline evaluates

.crow/weekly-patch-proposals.yaml

@@ -8,8 +8,26 @@
 # Global across platforms (the classifier groups over all of single_builds), so
 # a single job -- no matrix. Clones read-only; the only writes are the two
 # Forgejo issues via FORGEJO_TOKEN.
+#
+# Run manually with:
+#   crow pipeline create --branch main \
+#     --var weekly_patch_proposals=true devxy/build-cran-binaries
+#
+# The gate variable is `weekly_patch_proposals`, named after the pipeline: a
+# manual run instantiates every pipeline in `.crow/`, so one without its own
+# gate runs on *any* manual trigger in this repo. This one posts and edits
+# Forgejo issues, so an unrelated manual run must not fire it.
+variables:
+  weekly_patch_proposals:
+    description: 'Run the weekly failure triage. Also gates this pipeline.'
+    options:
+      - 'true'
+      - 'false'
+    default: 'false'
+
 when:
   - event: manual
+    evaluate: 'weekly_patch_proposals == "true"'
   - event: cron
     cron: weekly-patch-proposals