clippy: clear the workspace errors and apply the machine fixes

- Mark the raw-pointer interop entry points unsafe with # Safety docs
  (oak-core upload/download/frame-from-pixels, oak-audio convert) and
  satisfy the existing callers (tests).
- mut_from_ref: allow with the ABI contract documented (the handle
  get_mut helpers in oak-timeline/oak-render/oak-task take the shared
  reference the C ABI passes; exclusivity is the caller's unsafe
  contract).
- Fix the eq_op in the white-balance normalization (green / green).
- Apply cargo clippy --fix across the workspace (redundant closures and
  field names, field reassignment, items after test modules, ...).
- Revert the replace_box fix in image_effect's clip_define: a
  redefinition must allocate a new box, otherwise the old clip handle
  stays valid and the HS-map replace contract (clip != clip2) breaks.
- 283 warnings remain; they are all non-machine-applicable
  (chunks_exact -> as_chunks needs a manual iter_mut, too_many_arguments,
  complex types, missing Safety docs, ...) and are tracked as the
  follow-up.

crates/oak-task/tests/export_test.rs

@@ -69,7 +69,12 @@ fn build_project(media: &str) -> (Arc<Mutex<Project>>, NodeId) {
 		let (ccore, cbehavior) = oak_node::block::clip_create();
 		let clip = p.graph.add_node(ccore, cbehavior);
 		p.graph
-			.connect(footage, clip, oak_node::block::clip_input::TEXTURE_INPUT, -1)
+			.connect(
+				footage,
+				clip,
+				oak_node::block::clip_input::TEXTURE_INPUT,
+				-1,
+			)
 			.expect("connect footage to clip");
 		p.graph
 			.get_mut(clip)
@@ -207,7 +212,7 @@ fn export_writes_a_real_playable_mp4() {
 	let oak_core::texture::Texture::Cpu(frame) = &tex else {
 		panic!("decode produced a GPU texture");
 	};
-	let off = 32 * frame.linesize_bytes() as usize + 32 * 16;
+	let off = 32 * frame.linesize_bytes() + 32 * 16;
 	let r = f32::from_le_bytes(frame.data[off..off + 4].try_into().unwrap());
 	let g = f32::from_le_bytes(frame.data[off + 4..off + 8].try_into().unwrap());
 	assert!(