docs: update test counts in README

Reflect reduced test suite after batch mode removal (55 → 31 total, 45 → 21 fast).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -38,6 +38,6 @@ The Gradio interface launches at `http://localhost:7860`.
 ruff check .             # lint
 ruff format .            # format
 ty check                 # type check
-pytest -m "not slow"     # 45 fast tests
-pytest                   # all 55 tests (slow require CUDA + model download)
+pytest -m "not slow"     # 21 fast tests
+pytest                   # all 31 tests (slow require CUDA + model download)
 ```