feat(engine): clip move, clip effect_input, mandatory static FFmpeg

- oakengine_sequence_move_clip implemented for real (oaktimeline
  TrackMoveBlockCommand; fixes the graph-ownership/gap-anchor/ripple
  trim bugs the stub was hiding); same-track via the frozen C ABI,
  cross-track supported by the module command
- oaknode clip blocks now declare a tex_in texture input and set
  effect_input to it, so timeline clips can host effect chains; facade
  test covers effect insert/remove on a real clip
- oakffmpeg-link: FFMPEG_DIR is now mandatory with a clear panic (a
  Homebrew upgrade left the system ffmpeg .pc pointing at a deleted
  dav1d Cellar path, breaking links); reads a git-ignored workspace
  .env for IDEs that cannot inject env vars (RustRover); links the C++
  stdlib for C++ codec libs (svt-av1)
- oakengine re-exports oaknode so tests share one crate instance;
  it_node uses the direct instance's value type where it calls the
  module FFI (the --workspace dev-dependency feature split builds
  oaknode twice)

crates/oakcodec/src/timecodemetadata.rs

@@ -104,8 +104,7 @@ fn timecode_to_time(timecode: &str, timebase: &Rational, drop_frame: bool) -> Op
 		let m = real_fr_ts % frames_per10_minutes;
 
 		if m > drop_frames {
-			frame_count -= drop_frames
-				* ((m - drop_frames) / (llround(fr) * 60 - drop_frames));
+			frame_count -= drop_frames * ((m - drop_frames) / (llround(fr) * 60 - drop_frames));
 		}
 		frame_count -= drop_frames * 9 * d;
 	}