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/.env.example

@@ -9,19 +9,18 @@ GITEA_URL=http://localhost:3000
 GITEA_BOT_USER=rfc-bot
 GITEA_BOT_TOKEN=
 
-# The Gitea org or user that owns the meta repo and every RFC repo
-# the bot will create on graduation.
+# The Gitea org or user that owns every RFC repo the bot will create on
+# graduation.
 GITEA_ORG=wiggleverse
-META_REPO=meta
 
-# --- Multi-project registry (§22) ---
-# The registry repo (under GITEA_ORG) the framework reads to learn which
-# projects this deployment hosts. Optional through Slice M1: the registry
-# mirror lands in M3, and until then the single default project's content
-# repo is taken from META_REPO above. The repo's name is the deployment's
-# choice. When the mirror lands, REGISTRY_REPO becomes required and
-# supersedes META_REPO.
-# REGISTRY_REPO=wiggleverse-registry
+# §22.2 — the project registry repo (REQUIRED). The framework reads
+# `projects.yaml` at its root to learn which projects exist. The repo name is
+# the deployment's choice; the app fails to start if this is unset.
+REGISTRY_REPO=registry
+# §22.13 — optional id for the bootstrap/default project. Reserved for the
+# Plan B re-stamp; leave unset in Plan A (the default project id stays
+# `default`). When set, it must match an `id` in projects.yaml.
+# DEFAULT_PROJECT_ID=ohm
 
 # --- OAuth (Gitea) ---
 # In Gitea: Site Administration → Applications → Add OAuth2 Application.