v0.6.19 — Owned FP32 media scaling

The FP32 media encoder now obtains its owned work buffer from scaling, eliminating a separate copy while preserving lower-precision buffer reuse.

Eight-CPU full encoding of a decoded FP32 2048-square, 120-frame clip measured 15.145 seconds versus 17.342/17.627 second controls (about 13.4%). Complete MP4 bytes matched and full audio/video decoded. This is CPU encoding evidence; remote full-generation speedup remains unqualified.

No changes to model precision, codec, thread defaults, or hardware qualification. Focused media checks, clean source/wheel builds and bilingual documentation passed.