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/oaknode/src/track.rs

@@ -191,7 +191,11 @@ impl TrackBehavior {
 
 	/// Block strictly containing `time` (in < time < out; C++
 	/// `block_containing_time`).
-	pub fn block_containing_time(&self, time: oakcore_rs::Rational, blocks: &dyn BlockRange) -> Option<NodeId> {
+	pub fn block_containing_time(
+		&self,
+		time: oakcore_rs::Rational,
+		blocks: &dyn BlockRange,
+	) -> Option<NodeId> {
 		self.blocks
 			.iter()
 			.find(|b| blocks.contains_strict(**b, time))
@@ -200,7 +204,11 @@ impl TrackBehavior {
 
 	/// Block visible at `time` (in <= time < out; C++
 	/// `visible_block_at_time`).
-	pub fn visible_block_at_time(&self, time: oakcore_rs::Rational, blocks: &dyn BlockRange) -> Option<NodeId> {
+	pub fn visible_block_at_time(
+		&self,
+		time: oakcore_rs::Rational,
+		blocks: &dyn BlockRange,
+	) -> Option<NodeId> {
 		self.blocks
 			.iter()
 			.find(|b| blocks.contains(**b, time))
@@ -210,10 +218,7 @@ impl TrackBehavior {
 	/// Whether the [in, out) range holds no block or only a gap (C++
 	/// `is_range_free`).
 	pub fn is_range_free(&self, range: oakcore_rs::TimeRange, blocks: &dyn BlockRange) -> bool {
-		!self
-			.blocks
-			.iter()
-			.any(|b| blocks.overlaps(*b, range))
+		!self.blocks.iter().any(|b| blocks.overlaps(*b, range))
 	}
 
 	/// Total length (end of the last block; C++ `Track::get_length`).