feat(oakplugin): wire OpenFX plugins into the node graph and renderer

- oaknode: dynamic node factory registration, PluginNode value model
  pushing PluginJobPayload, traverser texture passthrough for texture
  inputs, type-stamped RefBox::get_checked.
- oakrender: PluginExecutor dependency-inversion slot; eval resolves
  and executes plugin jobs, purple frame on failure.
- oakplugin: node_factory with full OFX param -> node input
  translation (15 types, color semantics heuristic, combo ordering,
  secret/ui_group/ui_page, clip inputs), plugin instance registry,
  render executor + duplicator installation, progress reporter and
  active-viewer provider injection points, U8/U16/F16 input
  conversion with NaN scrubbing, in-place output frame writeback fix.
- gl_bridge.rs documents the wgpu<->GL interop spike: Metal-first on
  macOS rules out wgpu-hal GL interop; offscreen GL context deferred.

End-to-end tests cover registration, param translation, CPU render
pixel assertions, identity passthrough and NaN fallback.

crates/oakplugin/src/render.rs

@@ -129,7 +129,8 @@ pub fn texture_create(
 /// Rust 等价物。恒 0（GL suite 的 `OpenGLTextureIndex` 属性与
 /// render 驱动的 use_opengl 决策据此回退 CPU 路径；GPU 上传若落地
 /// 走 `oakrender::backend::GpuContextLike::upload` 的 wgpu token，
-/// 不暴露 GL id）。
+/// 不暴露 GL id）。真实化的评估与方案见 [`crate::gl_bridge`]
+/// （阶段 6a spike：方案 A 不可行，方案 B 暂缓）。
 pub fn texture_id(_texture: &Texture) -> i32 {
 	0
 }