Build-it-yourself model: bluebuild switch, no published image, drop CI workflow

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

recipes/recipe.yml

@@ -46,6 +46,8 @@ modules:
           - org.godotengine.Godot
           - org.videolan.VLC
 
-  # Installs the cosign public key + container signature-verification policy
-  # so `bootc`/`rpm-ostree` signed rebases work. Requires cosign.pub at repo root.
+  # Installs the cosign public key + container signature-verification policy.
+  # Unused in the current build-locally model (`bluebuild switch` rebases from a
+  # local oci-archive, unsigned) — kept so publishing to a registry later only
+  # requires a push, not a recipe change. Requires cosign.pub at repo root.
   - type: signing