Enhancing --margin to support negative offsets

[vini14zin]

Hello!

I'd like to suggest a small but powerful change to the --margin parameter: allowing it to accept negative numbers.

The Use Case: > Sometimes, even with a high threshold, there's a bit of "trailing silence" or breath at the end of a sentence that makes the edit feel a bit slow. A negative margin would allow us to "shave off" a few milliseconds from the start and end of every detected loud segment, resulting in a snappier, more professional-sounding edit.

Example: > auto-editor video.mp4 --margin -0.05s

This would be a great quality-of-life improvement for creators who want that "ultra-fast" pacing.

[WyattBlue]

We support this already