workspace: zero compiler warnings across all targets

254 warnings (320 counting replayed-cache re-emitters) cleaned:
unused mut/imports/variables, irrefutable if-lets and unreachable
patterns, dead code removed or annotated #[allow(dead_code)] with
the reason (C++ parity value sets, cfg(test) helpers, public API
reservations), drop(&ref) no-ops removed, fn-pointer identity via
std::ptr::fn_addr_eq, the test-stubs feature declared in
oak-node's manifest, missing docs filled. Every unused-Result site
was judged individually: meaningful errors propagate, intentional
ignores are let _ = with a note.

Two pre-existing latent bugs are documented in place, behavior
preserved: app.rs's timeline-tool observer and dialogs.rs's format
subscription both drop the returned Subscription immediately, so
they never fire.

crates/oak-plugin/src/host.rs

@@ -276,8 +276,6 @@ fn global_ofx_host() -> *mut OfxHost {
 
 /// kOfxActionLoad。
 pub(crate) const ACTION_LOAD: &str = "OfxActionLoad";
-/// kOfxActionUnload。
-pub(crate) const ACTION_UNLOAD: &str = "OfxActionUnload";
 /// kOfxActionDescribe。
 pub(crate) const ACTION_DESCRIBE: &str = "OfxActionDescribe";
 /// kOfxActionCreateInstance。
@@ -552,8 +550,6 @@ pub(crate) const PROP_CLIP_COLOURSPACE: &str = "OfxImageClipPropColourspace";
 /// kOfxImageClipPropPreferredColourspaces（ofxColour.h:201）：clip 偏好
 /// 色彩空间（GetClipPreferences 的 out args 可写）。
 pub(crate) const PROP_CLIP_PREFERRED_COLOURSPACES: &str = "OfxImageClipPropPreferredColourspaces";
-/// 工作空间（任务要求：全链路 ACEScg）。
-pub(crate) const WORKING_COLOURSPACE: &str = "ACEScg";
 /// 宿主支持的 native 色彩配置标识（ofxColour.h:78 的唯一现行值）。
 pub(crate) const NATIVE_CONFIG_ID: &str = "ofx-native-v1.5_aces-v1.3_ocio-v2.3";
 /// 宿主 OCIO 配置 URI（ofxColour.h:110 允许 ocio:// 内建配置；本宿主

crates/oak-plugin/src/node_factory.rs

@@ -1304,7 +1304,7 @@ mod tests {
 		) -> i32 {
 			0
 		}
-		let mut def = ParamDef::new("curve", ofx::TYPE_PARAMETRIC);
+		let def = ParamDef::new("curve", ofx::TYPE_PARAMETRIC);
 		def.props
 			.set_one(ofx::PROP_LABEL, PropValue::String(CString::new("Curve").unwrap()));
 		def.props

crates/oak-plugin/src/param.rs

@@ -362,7 +362,7 @@ impl ParamDef {
 	/// 按 OFX 类型构建定义（镜像 HS ofxhParam.cpp:224-352：
 	/// universalProps + addStandardParamProps 的分类型属性表）。
 	pub(crate) fn new(name: &str, ofx_type: &str) -> Self {
-		let mut props = PropertySet::new();
+		let props = PropertySet::new();
 		let uname = name.to_string();
 		let utype = ofx_type.to_string();
 

crates/oak-plugin/src/suites/image_effect.rs

@@ -505,7 +505,7 @@ mod tests {
 	/// 重复定义整体替换（HS map 覆盖）。
 	#[test]
 	fn describe_clip_define_and_props() {
-		let mut desc = EffectDescriptor::new();
+		let desc = EffectDescriptor::new();
 		let s = suite_v1();
 		let h = descriptor_handle(&desc);
 

crates/oak-plugin/src/suites/interact.rs

@@ -490,10 +490,6 @@ mod tests {
 	use std::ffi::{c_char, CStr};
 	use std::sync::Mutex;
 
-	fn cs(s: &str) -> CString {
-		CString::new(s).unwrap()
-	}
-
 	/// interact 属性表：PixelScale/ViewportSize/SuggestedColour/
 	/// SlaveToParam/BitDepth/HasAlpha 等按头文件预置，经 property suite
 	/// 可读写。

crates/oak-plugin/src/suites/memory.rs

@@ -81,17 +81,6 @@ pub(crate) fn free(ptr: *mut u8) -> bool {
 	}
 }
 
-/// 兜底回收全部在账块（destroyInstance 的泄漏防线）。返回回收块数
-/// （泄漏断言用）。
-pub(crate) fn sweep_leaked() -> usize {
-	let mut ledger = lock();
-	let n = ledger.len();
-	for b in ledger.drain(..) {
-		unsafe { std::alloc::dealloc(b.ptr as *mut u8, b.layout) };
-	}
-	n
-}
-
 /// 函数表布局（与 SDK `OfxMemorySuiteV1` 一致；`size_t` 在本平台
 /// 与 `usize` 同宽，stable Rust 用 `usize` 表达——骨架的 `c_size_t`
 /// 是不稳定特性，弃用）。

crates/oak-plugin/src/suites/mod.rs

@@ -212,9 +212,6 @@ pub(crate) fn gl_ctx() -> Option<GlCtx> {
 	GL_CTX.with(|c| c.borrow().clone())
 }
 
-/// 宿主进程身份（fetchSuite 的 version 检查用；= OFX API 1.5）。
-pub(crate) const OFX_API_VERSION: i32 = 105;
-
 /// fetchSuite 宿主入口：按名字与版本返回函数表指针；不认识或版本
 /// 不符返回 `None`（FFI 层转 NULL）。
 ///

crates/oak-plugin/src/suites/multithread.rs

@@ -260,7 +260,6 @@ pub fn suite_v1() -> &'static MultiThreadSuiteV1 {
 mod tests {
 	use super::*;
 	use std::sync::atomic::{AtomicUsize, Ordering};
-	use std::sync::Mutex;
 
 	/// 每个插件线程把 (index, count) 累计进 userdata。
 	unsafe extern "C" fn worker(index: c_uint, count: c_uint, arg: *mut c_void) {

crates/oak-plugin/src/suites/param.rs

@@ -787,7 +787,7 @@ mod tests {
 
 	/// 用 paramDefine 建一个实例（describe 产物 → createInstance）。
 	fn make_instance() -> (Arc<Instance>, *mut c_void) {
-		let mut desc = EffectDescriptor::new();
+		let desc = EffectDescriptor::new();
 		let s = suite_v1();
 		let dhandle = descriptor_handle(&desc);
 		unsafe {
@@ -836,7 +836,7 @@ mod tests {
 
 	#[test]
 	fn describe_define_and_get() {
-		let mut desc = EffectDescriptor::new();
+		let desc = EffectDescriptor::new();
 		let s = suite_v1();
 		let handle = descriptor_handle(&desc);
 		let t = cs("OfxParamTypeDouble");

crates/oak-plugin/src/suites/parametric.rs

@@ -42,10 +42,8 @@
 //!   BadHandle/BadIndex）。
 
 use std::borrow::Cow;
-use std::ffi::{c_char, c_double, c_int, c_void};
+use std::ffi::{c_double, c_int, c_void};
 
-use crate::descriptor::EffectDescriptor;
-use crate::instance::Instance;
 use crate::param::{ParamDef, ParamInstance, ParamValue};
 use crate::param_curve::Curve;
 use crate::property::{PropertySet, Value};
@@ -414,10 +412,12 @@ pub fn suite_v1() -> &'static ParametricParameterSuiteV1 {
 #[cfg(test)]
 mod tests {
 	use super::*;
-	use std::ffi::CString;
+	use std::ffi::{c_char, CString};
 	use std::sync::Arc;
 
+	use crate::descriptor::EffectDescriptor;
 	use crate::host::Plugin;
+	use crate::instance::Instance;
 	use crate::param::{ParamInstance, ParamSetInstance};
 	use crate::property::PropertySet;
 

crates/oak-plugin/src/suites/property.rs

@@ -498,7 +498,7 @@ unsafe extern "C" fn prop_get_string(
 			let r = get_string(set, name, index);
 			if std::env::var_os("OAK_OFX_TRACE").is_some() {
 				let rendered = match &r {
-					Ok(p) => format!("0 <- {:?}", unsafe { std::ffi::CStr::from_ptr(*p) }),
+					Ok(p) => format!("0 <- {:?}", std::ffi::CStr::from_ptr(*p)),
 					Err(c) => format!("{c}"),
 				};
 				eprintln!("[ofx] propGetString(h={handle:p}, {name}[{index}]) -> {rendered}");