annotate_frame draws Chinese labels (e.g. '确认摔倒 P-0001') using a CJK
font via Pillow when available (Windows uses Microsoft YaHei), and falls
back to the ASCII cv2 label when Pillow or a CJK font is missing. 86 tests
pass.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>