Session produced a working prototype (docs/map_vision_wip.py, not
wired into the app yet) for the image-based map-screenshot marker
pipeline: label OCR, pitch estimation from label spacing, a matched-
filter grid-intersection detector, whole-grid crossing prediction, and
RANSAC homography fitting, each validated against real screenshots
with diagnostic images along the way.
Found a real remaining bug before pausing: crossings are currently
all predicted from one single reference label using one global pitch,
so predictions drift with distance from that reference under genuine
perspective distortion (confirmed: ~2-4 degree measured tilt, not
noise). Documented the fix (BFS grid-growing: expand one cell at a
time from every confirmed point, using local rather than global
spacing) as the next step, not yet implemented.
