feat(registry): hard-cut META_REPO -> REGISTRY_REPO; wire mirror into startup/webhook/sweep

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

backend/app/main.py

@@ -31,6 +31,7 @@ from . import (
     projects,
     providers as providers_mod,
     ratelimit,
+    registry as registry_mod,
     turnstile,
     webhooks,
 )
@@ -100,8 +101,23 @@ async def lifespan(app: FastAPI):
     config = load_config()
     db.run_migrations(config)
     db.init(config)
-    projects.seed_default_project(config)  # §22.13 step 1
     gitea = Gitea(config)
+    # §22.2: mirror the registry before anything reads projects/content_repo.
+    # First boot has no last-good rows, so a missing/invalid registry is fatal
+    # (loud-fail per separation-of-concerns); the reconciler sweep keeps it
+    # fresh thereafter and tolerates a later bad PR.
+    try:
+        await registry_mod.refresh_registry(config, gitea)
+    except Exception as e:
+        raise RuntimeError(
+            f"registry mirror failed at startup ({config.registry_repo_full}/projects.yaml): {e}"
+        ) from e
+    if projects.default_content_repo(config) is None:
+        raise RuntimeError(
+            f"registry does not describe the default project "
+            f"{projects.resolved_default_id(config)!r} (no content_repo). "
+            f"Add it to {config.registry_repo_full}/projects.yaml."
+        )
     bot = Bot(gitea)
     reconciler = cache.Reconciler(config, gitea)
     digest_sched = digest.DigestScheduler()
@@ -130,7 +146,7 @@ async def lifespan(app: FastAPI):
     reconciler.start()
     digest_sched.start()
     hygiene_sched.start()
-    log.info("RFC app started — meta repo %s/%s", config.gitea_org, config.meta_repo)
+    log.info("RFC app started — registry %s", config.registry_repo_full)
     try:
         yield
     finally: