[alex-mextner]

Refs #757

Cause

The K1 SE camera rides on the toolhead, so after a job the same empty plate is seen shifted (~100 px, a few % zoom) from where the reference was taken. The 2026-11-13 preflight frames (20:37 / 20:38) show the plate on and empty; the only reference at the time (Z 125.0) was taken from yet another place. Compared pixel by pixel that read ~70% of the plate surface changed -> plate missing -> preflight FAIL, start refused, and bed check --assume-empty refuses a plate-missing verdict so it could not override. Not Z (124.8 vs 125.0 is within tolerance), LED or thresholds.

Change

lib/bed_pose.py locates the frame against its reference first, by the scene round the bed region (what a plate or part cannot change):

• same view (a fixed camera, any light): judged as before
• moved (SIFT homography, scene lines up): the frame is warped onto the reference and judged there; evidence masks are mapped back onto the camera frame
• lost: the frame was not judged, so EVERY verdict (a clear bed with the plate on too, never a PASS) becomes unknown (preflight WARN) with the fix: 3d printer bed reference NAME --capture from where the camera is now (check the watch.bed.roi outline), or put the toolhead back
• a --no-plate reference from another view is not used; a frame judged from a moved/lost camera never becomes the reference by itself (bed_refs.refresh_refusal)

Evidence

Real saved frames in tests/data/bed/k1se_*.jpg (camera frames of 2026-11-13, scaled to 640 px).

Tests

tests/test_bed_pose.py: 30 tests, e.g. both preflight frames against the old reference give unknown/WARN with the fix; the 20:37 frame passes against the 20:38 reference from ~100 px away; a plate taken off and a part on the plate still FAIL, also with the camera moved or zoomed; U1 parts/spaghetti/night light are never lost; empty/whole-frame ROI. With the pose check disabled the lost-pose test fails fail. pytest tests/test_bed_*.py: 591 passed.

Not done / follow-ups

bed reference k1se --capture from the idle view must wait until the running print ends; do not move the bed meanwhile. Review notes not addressed: a MOVED frame judges only the part of the bed region the moved frame still covers (>= 90 %), no bin/3d e2e test.