Stored analysis overlays now use the decoded frame; latch resets and draw failures surface. Verified with bare-video, replay-wiring, visual_policy, and analysis-progress tests.
The selector now returns candidate locations with an activity flag, so the quiet half of
the finger's sampling grid can be drawn at last: one radius-1 dot per candidate, in the
idle tint and off the flow ramp, on no sample that also carries an arrow. The dots are
`DRAW_IDLE_GRID_DOTS` (on) and `draw_arrow_display(idle_dots=...)`; box and mini keep
their own SDK path.
The selector returned only the arrows it would draw, so a view could not draw
anything at a quiet sample and the below-threshold branch was unreachable. It
now returns every candidate location plus an `active` flag, both callers filter
on it, and the magnitude colour ramp is fixed so one magnitude is one colour
across frames. Verified by pixel parity against HEAD for the 2D canvas and the
3D overlay, and by the shared and studio suites.
ykcheungab