feat(kebab-core): p9-fb-23 task 2 — CanonicalDocument gains last_chunker_version + last_embedding_version

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/kebab-store-sqlite/tests/list_docs.rs

@@ -67,6 +67,8 @@ fn make_doc(
         parser_version: ParserVersion("test".into()),
         schema_version: 1,
         doc_version: 1,
+        last_chunker_version: None,
+        last_embedding_version: None,
     };
     (asset, doc)
 }