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/src/eval.rs

@@ -559,7 +559,7 @@ impl RenderEvalHooks {
         in_flight: &mut HashSet<usize>,
     ) -> NodeValue {
         let mut payload = payload.clone();
-        for (_, value) in payload.params.iter_mut() {
+        for value in payload.params.values_mut() {
             self.resolve_value(value, depth, in_flight);
         }
         match self.process_shader_job(&payload) {
@@ -584,7 +584,7 @@ impl RenderEvalHooks {
         in_flight: &mut HashSet<usize>,
     ) -> Option<NodeValue> {
         let mut payload = payload.clone();
-        for (_, value) in payload.values.iter_mut() {
+        for value in payload.values.values_mut() {
             self.resolve_value(value, depth, in_flight);
         }
 
@@ -843,7 +843,7 @@ impl RenderEvalHooks {
                         return None;
                     }
                     let nested = (unsafe { oak_node::jobs::shader_job(handle) }).cloned()?;
-                    Some(self.process_shader_job_depth(&nested, depth + 1)?)
+                    self.process_shader_job_depth(&nested, depth + 1)
                 });
             let tex = tex?;
             let (token, tex_size) = match &tex {
@@ -1797,7 +1797,7 @@ fn blend_transition(
     // Fallback: without a blend (a missing side, or a shader job that
     // could not run) show the side that natively covers `time` — the
     // outgoing block before the cut, the incoming one at or after it.
-    Ok(blended.or_else(|| if progress < 0.5 { from } else { to }))
+    Ok(blended.or(if progress < 0.5 { from } else { to }))
 }
 
 /// Walk an adjustment block's effect chain to its head: the first node