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-tui/tests/inspect.rs

@@ -91,6 +91,8 @@ fn make_doc() -> CanonicalDocument {
         parser_version: ParserVersion("test-parser".into()),
         schema_version: 1,
         doc_version: 1,
+        last_chunker_version: None,
+        last_embedding_version: None,
     }
 }