Add platform support note and existing file handling documentation to README and skill docs, clarifying Windows 11-only testing, per-script ffmpeg/ffprobe requirements, and file replacement behavior with -y flag across Clone-Image.md, Clone-Video.md, Compare-Videos.md, Crop-Clips.md, Get-VideoAudio.md, SKILL.md and index.md

skill/Crop-Clips.md

@@ -115,6 +115,7 @@ An invalid `-Size` value fails immediately, before any file is processed.
 - Preserves original quality and audio
 - **In-place mode** (source and target are the same directory). This is the default when `-Source` and `-Target` are both omitted, because both default to the current directory:
     - Each original `video.mp4` is copied to `video.bak.mp4`. An existing `.bak.mp4` is replaced.
+    - Only files that are cropped are backed up. A file that is skipped, because it is already at the requested size or its resolution is not in the table, keeps its existing `.bak.mp4`. Re-running in place without `-Size` skips the files it already cropped, so the backup stays the original. A re-run with a different `-Size` crops them again, and replaces the backup with the first run's output. Keep your own copy of the originals before a re-run with a different `-Size`, or use a separate `-Target` folder.
     - The cropped result is written to `video.crop.mp4`. Only after that succeeds is the original `video.mp4` deleted and replaced by the cropped file. The `.bak.mp4` backup is kept.
     - Run with `-WhatIf` first, and do not run it on a folder you have not designated.
 - **Separate target folder**: the source files are not changed. A file with the same name already in the target folder is deleted and replaced.