Add comprehensive existing file handling documentation to Create-Clip.md, Create-PillarBox.md, Create-Turnaround.md and Get-LastFrame.md explaining ffmpeg -y replacement behavior and WhatIf safety recommendations, expand SKILL.md prerequisites section to clarify Windows 11-only platform support with pwsh.exe requirement and reorganize core vs optional tools with task-specific check guidance, update conventions section to add Frames/Frame syntax tables and .skip marker behavior details, replace safety

skill/Create-Turnaround.md

@@ -240,6 +240,13 @@ cd C:\renders\CharacterA
 .\Create-Turnaround.ps1 -Source .\renders -Target turnaround.webp -Quality 1 -Compression 6
 ```
 
+## Existing Files
+
+An existing `-Target` image is **replaced** without a prompt. ffmpeg runs with `-y`.
+
+- The folder that contains `-Target` must already exist. The script stops with an error instead of creating it.
+- Use `-WhatIf` first, or write to a new name.
+
 ## Safe Execution
 
 This script supports `-WhatIf` and `-Confirm` for safe execution: