docs(testing): document new run_tests_batched.py in Running Tests section

docs/guide_testing.md

@@ -437,6 +437,16 @@ uv run pytest tests/test_command_palette.py -v
 uv run pytest tests/test_command_palette.py::test_fuzzy_match_prefix_ranks_first -v
 ```
 
+### Batched Run (Categorized)
+
+```bash
+uv run python scripts/run_tests_batched.py
+```
+
+This runs the new categorized batcher: 6 fixture-class-isolated tiers (opt-in skipped by default, unit with xdist, mock_app, live_gui in one session, headless, performance). Each tier prints a summary line. Use `--plan` to see the batch plan without running; `--audit` to list unclassified files; `--tiers 1,2` to limit which tiers run.
+
+See `conductor/tracks/test_batching_refactor_20260606/spec.md` for the full design.
+
 ### By Marker
 
 ```bash