denoise.md §4.4 requires the training repo to read photosites through
dr-decode, not LibRaw, so black and white levels, the active area and the
CFA phase match what the app will feed the network. mosaic_dump reads
`input<TAB>prefix` lines and writes the whole readout as .npy plus a JSON
of what decode and metadata report. The masked border is kept: its
optically black photosites are a free dark frame for the noise profile.