Add expand_palette_to_rgb() for converting palette indices to RGB using the color map (1/2/4/8/16-bit indices, row-aligned sub-byte).
Accept CIE L*a*b* (photometric=8) as Lab(8) for 8-bit 3-channel images. Re-bias a/b from signed to unsigned during expand_chunk so callers handle CIELab and ICCLab the same way.
Treat TransparencyMask as grayscale instead of erroring.
Handle missing LZW end-of-information code gracefully when output was already produced.
aarshivv