fix(tests): gate test_search_lancedb_capability behind RUN_HEAVY

These tests call run_search() which triggers _connect_lancedb() ->
import lancedb -> LanceDBBackgroundEventLoop daemon thread. On CI
(Ubuntu) the thread race-conditions with Kuzu C++ queries causing a
segfault. On macOS the race didn't manifest due to timing differences.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: HumanBean17

tests/test_search_lancedb_capability.py

@@ -1,14 +1,22 @@
 """`run_search` with `capability=` — exercises Lance `array_has` + vector path (no CocoIndex)."""
 from __future__ import annotations
 
+import os
 import uuid
 
+import pytest
+
 from sentence_transformers import SentenceTransformer
 
 from ast_java import ONTOLOGY_VERSION
 from index_common import SBERT_MODEL
 from search_lancedb import TABLES, _query_vector, run_search
 
+pytestmark = pytest.mark.skipif(
+    os.environ.get("JAVA_CODEBASE_RAG_RUN_HEAVY", "").strip() != "1",
+    reason="imports lancedb at runtime (spawns background thread that causes Kuzu segfaults)",
+)
+
 
 def _one_java_row_built_for_capability_filter(
     *,