The 2× focal-length collision test wasn't actually colliding (adjacent IR
pixels rounded to different RGB columns). 4× makes them collapse, so the
np.minimum.at reduce is now exercised. Also drop unused H_ir, W_ir.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Forward-project IR depth pixels into the RGB pixel grid with a z-buffer.
Output uint16 mm at RGB resolution, ready to feed SAM21.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>