Add: Banner, usage description to iccSpecSepToTiff

[ChrisCoxArt]

Add more detailed usage description.
Make pointer usage safer.
Fix inconsistent indention.
Make some variable names more descriptive.
Add additional safety to start/end/step inputs.
Add a few comments to explain what the code is doing.
Fixes #387

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[xsscx]

Mon Jan 5 03:48:34 AM UTC 2026

[xsscx]

PR Summary

Tools/IccSpecSepToTiff/iccSpecSepToTiff

Usage: iccSpecSepToTiff output compress sep infile_fmt start end incr {profile}
Concatenates several spectral TIFF files into a single file, with optional embedded ICC profile.
output: path/name of the TIFF file to be created
compress: boolean (0 | 1), should the output be compressed
sep: boolean (0 | 1), plane data be seperated in the output TIFF
infile_fmt: printf format string for input files, example: "spec_%06d.tiff"
start: integer, first channel number to process
end: integer, last channel number to process
increment: integer, increment between channels
profile: optional ICC profile to embed in the output TIFF