ft-hands keeps the last 12 s of hand crops (each view's landmark crop, 1.6x, at most
224 px), its hands, gestures and landmarks in RAM (track/flagbuf.h, HANDS_FLAG_BUFFER=1).
`ft-handsctl flag [note]` asks for them through run_dir/flag; ft-hands writes them and the
next 2 s to HANDS_FLAG_DIR/flag-<time> from a low-priority thread, for frame-hands'
offline tools. ft-handsctl also saves a /dev/video99 frame and ft-handview's head poses,
and the drawn hands pulse cyan when a flag is taken (ft-handview's new flash and poses
commands). ft-handreplay --flag-at/--flag-every makes the same flags from recordings.
Measured on a replayed ring: +58 MB peak RSS, 0.1 ms a crop on an A720 (about 1% of a
core). Unit tests: tests/flagbuf_test.cpp (make check), tests/test_handsflag.py.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
