phase: 94_ls_tree_drilldown

All green. Verification complete.

**Phase 94 — `ls` drill-down tree: final verification pass (all 5 tasks were already complete; verified, nothing to fix)**

- Verified `ls` 3-level tree (`app/rag/agent.py`): `ls()` sources + summaries, `ls(source)`/`ls(source/folder)` drill-down, 50-line file cap + grep-pointer note, NOT-A-FOLDER teaching refusal
- Verified `folder_summaries` (migration 0017, model, `app/rag/folder_summaries.py` generator: `FOLDER_SUMMARY_MODE` marker, fail-soft per folder, ≥2-doc scope + prune) wired change-gated in both sync paths
- Verified 10-turn fixture battery verdict recorded in `TOOL_CALLING_TESTING.md` §9 (2026-09-11): turbo PASS 19/19 contract, 98.7 s (−12.5…−13.2 % vs baseline); lite PASS 18/18, 43.6 s (+7.7 %) — accuracy at/above baseline, gate met
- `uv run pytest --cov=app --cov-report=term-missing` → 1939 passed, 0 failed; TOTAL coverage **99 %** (folder_summaries.py 100 %)
- `uv run ruff check .` → clean; `uv run pyright` → 0 errors, 0 warnings
- E2E in isolation: `test_ls_tree_drilldown.py` 3 passed; `test_agent_document_tools` 4, `test_agent_unlimited_tools` 4, `test_harness_aligned_tools` 3, `test_search_tool` 3, `test_grep_regex_teaching` 2, `test_response_to_docs` 4 — all passed (read/grep contracts untouched)
- Dedicated folder-summary tests (fail-soft, prune, both sync paths, migration): 46 passed
- Completion criteria: all 6 met; working tree holds only phase-94 changes (commit left to harness per protocol)

**Next pending phase:** `95_read_truncation_cap`

tests/unit/test_sync_button.py

@@ -752,8 +752,9 @@ def _patch_sync_seams(
     """The runner's seams, monkeypatched on ``app.api.sync`` (the house
     mock-import pattern): fresh settings (no ``.env`` leak), a no-op
     model probe, a sentinel LLM client, one git row, the gated clone +
-    import, a no-op overview, and the DB-free sources-version step
-    (dummy session + pinned counters)."""
+    import, a no-op overview, a no-op folder-summary step (phase 94 —
+    the sentinel LLM client has no ``chat``), and the DB-free
+    sources-version step (dummy session + pinned counters)."""
     monkeypatch.setattr(
         sync_api,
         "get_settings",
@@ -783,6 +784,13 @@ def _patch_sync_seams(
 
     monkeypatch.setattr(sync_api, "regenerate_overview", fake_overview)
 
+    async def fake_folder_summaries(
+        db: object, llm: object, *, skip: bool = False
+    ) -> dict[str, int]:
+        return {"generated": 0, "failed": 0, "pruned": 0}
+
+    monkeypatch.setattr(sync_api, "generate_folder_summaries", fake_folder_summaries)
+
     class _DummySession:
         def close(self) -> None:
             pass