Hardened the optional LLM extraction path

src/repo_registry/core/service.py

@@ -127,7 +127,20 @@ class RegistryService:
             chunks,
         )
         stored_chunks = self.store.list_content_chunks(repository_id, completed_run.id)
-        candidates = self._generate_candidates(repository, facts, stored_chunks)
+        try:
+            candidates = self._generate_candidates(repository, facts, stored_chunks)
+        except Exception as exc:
+            self.store.create_review_decision(
+                repository_id,
+                completed_run.id,
+                action="llm_extraction_failed",
+                notes=str(exc),
+            )
+            candidates = self.candidate_generator.generate(
+                repository,
+                facts,
+                stored_chunks,
+            )
         self.store.replace_candidate_graph(repository_id, completed_run.id, candidates)
         return ScanSummary(
             analysis_run=completed_run,