add Test docs for OS and Pro (#14750)

* add Test docs for OS and Pro

* docs: fix case-mismatch image filenames breaking Hugo build

Four image references used capital "T" (Tests_ss*.png) but the actual
files are lowercase (tests_ss*.png). On case-sensitive Linux CI, Hugo
could not resolve the resource and render-image.html crashed on
$r.MediaType.SubType.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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Co-authored-by: Paul Osinski <42211303+paulOsinski@users.noreply.github.com>
Co-authored-by: Paul Osinski <posinski34@gmail.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-authored-by: Cody Maffucci <46459665+Maffooch@users.noreply.github.com>

Author: 4 people