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-render/examples/render_audio_wav.rs

@@ -12,7 +12,9 @@ use oak_render::ticket::{AudioTicketParams, MontageClip, TicketPayload};
 fn main() {
 	let args: Vec<String> = std::env::args().collect();
 	if args.len() < 6 {
-		eprintln!("usage: render_audio_wav <media> <stream_index> <start_sec> <end_sec> <out.wav> [fps]");
+		eprintln!(
+			"usage: render_audio_wav <media> <stream_index> <start_sec> <end_sec> <out.wav> [fps]"
+		);
 		std::process::exit(64);
 	}
 	let media = &args[1];
@@ -20,7 +22,11 @@ fn main() {
 	let start_sec: f64 = args[3].parse().unwrap();
 	let end_sec: f64 = args[4].parse().unwrap();
 	let out_path = &args[5];
-	let fps: i64 = if args.len() > 6 { args[6].parse().unwrap() } else { 25 };
+	let fps: i64 = if args.len() > 6 {
+		args[6].parse().unwrap()
+	} else {
+		25
+	};
 
 	let sample_rate = 48000i32;
 	let channel_layout = 0x3u64; // stereo
@@ -58,7 +64,7 @@ fn main() {
 			other => {
 				eprintln!("frame {f}: render failed: {:?}", other.is_err());
 				let frames = ((sample_rate as f64) / fps as f64).round() as usize;
-				pcm.extend(std::iter::repeat(0i16).take(frames * channels));
+				pcm.extend(std::iter::repeat_n(0i16, frames * channels));
 			}
 		}
 	}