feat(metadata): strip container metadata from WebM/MP3/WAV/FLAC/OGG via ffmpeg (v0.6.4)

remove_ai_metadata now handles non-ISOBMFF audio/video (which the box walker
can't reach) by shelling out to ffmpeg with a lossless stream copy
(`-map_metadata -1 -map_chapters -1 -c copy`): codec data is untouched, only
container tags/chapters (ID3 / RIFF / Vorbis comments / EBML tags) are dropped.
Requires ffmpeg on PATH; raises a clear RuntimeError if absent or if ffmpeg
can't parse the input (instead of crashing in the image path).

Verified end-to-end: a real ffmpeg-made WAV/MP3 with a "Suno AI" title tag ->
tag gone, audio bytes preserved.

NOT built (evaluated, deliberate): Resemble PerTh audio *detection* --
`get_watermark()` returns a raw bit array with no presence/confidence flag, so
reliably telling watermarked from clean needs Resemble's fixed payload or a
confidence API (neither public; no real sample to calibrate). Same wall as the
SynthID pixel detector. AVIF/HEIF meta-box EXIF/XMP stripping also stays a gap
(needs exiftool, a non-installed binary). Both documented in CLAUDE.md.

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

uv.lock

@@ -2865,7 +2865,7 @@ wheels = [
 
 [[package]]
 name = "remove-ai-watermarks"
-version = "0.6.3"
+version = "0.6.4"
 source = { editable = "." }
 dependencies = [
     { name = "click" },