- processor.rs: resample/channel-convert/time-stretch now runs an
in-process FFmpeg filter graph (abuffer -> atempo -> aformat ->
abuffersink) via ffmpeg-next
- waveform.rs: extraction decodes through oakcodec's FFmpegDecoder
(interleaved f32) instead of the fb_decoder/fb_audio_graph pair
- bridge/ffmpeg.rs and the null fb_* test stubs deleted;
oakcommon::ffmpegutils bridge constants become plain ints
- liboakengine.dylib no longer imports any fb_* symbol (nm -u clean);
the remaining runtime imports are the host-provided oakcore_* symbols
- real decode/resample tests added (generated PCM input, no network)