fix(registry): clean content_repo failure in hygiene; retire META_REPO from .env.example; clarity + idempotency test

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/hygiene.py

@@ -299,7 +299,14 @@ async def _delete_branch_via_bot(
         log.warning("hygiene: cannot delete %s/%s — slug missing from cache", slug, branch)
         return False
     if not rfc["repo"]:
-        owner, repo = config.gitea_org, (projects_mod.default_content_repo(config) or "")
+        repo = projects_mod.default_content_repo(config)
+        if not repo:
+            log.warning(
+                "hygiene: default project has no content_repo; skipping branch delete for %s/%s",
+                slug, branch,
+            )
+            return False
+        owner = config.gitea_org
     elif "/" in rfc["repo"]:
         owner, repo = rfc["repo"].split("/", 1)
     else:

backend/app/webhooks.py

@@ -80,16 +80,21 @@ def make_router(config: Config, gitea: Gitea) -> APIRouter:
             payload = {}
         repo_full = (payload.get("repository") or {}).get("full_name") or ""
         registry_full = f"{config.gitea_org}/{config.registry_repo}"
-        meta_repo = projects_mod.default_content_repo(config)
-        meta_full = f"{config.gitea_org}/{meta_repo}" if meta_repo else None
+        content_repo = projects_mod.default_content_repo(config)
+        if not content_repo:
+            log.warning("webhook: default project content_repo is unknown; corpus refresh skipped")
+        content_full = f"{config.gitea_org}/{content_repo}" if content_repo else None
         try:
             if repo_full == registry_full:
                 # §22.2: a registry-repo push re-mirrors the projects table.
+                # Tolerate a malformed projects.yaml (keep last-good rows); let a
+                # transport error bubble to the outer 500 so an unreachable Gitea
+                # on a registry push is loud rather than silently dropped.
                 try:
                     await registry_mod.refresh_registry(config, gitea)
                 except registry_mod.RegistryError:
                     log.exception("registry webhook: invalid projects.yaml; keeping last-good")
-            elif meta_full and (repo_full == meta_full or not repo_full):
+            elif content_full and (repo_full == content_full or not repo_full):
                 await cache.refresh_meta_repo(config, gitea)
                 await cache.refresh_meta_branches(config, gitea)
                 await cache.refresh_meta_pulls(config, gitea)