feat(render): dynamic OpenGL/Vulkan backend split and backend-neutral viewer

- Extract libolive-rendercore static library to minimize backend link boundary.
- Add DynamicRenderer adapter with C ABI (oakgl/oakvulkan shared libs).
- Make OAK_ENABLE_DYNAMIC_RENDER_BACKEND default ON with OpenGL fallback.
- Implement VulkanRenderer prototype (textures, shaders, UBO blit, readback).
- Add backend-neutral viewer readback path (offscreen -> QImage -> QPainter).
- Refactor PluginRenderer to be renderer-agnostic; OFX plugins fall back to CPU
  path on non-OpenGL backends while preserving OpenGL render path.
- Add Renderer::AttachOutputTexture/DetachOutputTexture and C ABI forwards.
- Update docs/zh/render-backend-dynamic-plan.md for Phase 3/4/5.

app/render/backend/dynamicrenderer.cpp

@@ -45,6 +45,8 @@ QString DynamicRenderer::LibraryFilename() const
 	const QStringList candidates = {
 		app_dir.filePath(filename),
 		app_dir.filePath(QDir(QStringLiteral("render_backends")).filePath(filename)),
+		app_dir.filePath(QDir(QStringLiteral("../lib")).filePath(filename)),
+		app_dir.filePath(QDir(QStringLiteral("../../lib")).filePath(filename)),
 		app_dir.filePath(QDir(QStringLiteral("../app")).filePath(filename)),
 		app_dir.filePath(QDir(QStringLiteral("../../app")).filePath(filename))
 	};
@@ -139,6 +141,10 @@ bool DynamicRenderer::ResolveFunctions()
 	RESOLVE(get_pixel_from_texture_, OakBackendGetPixelFromTextureFn,
 			"oak_renderer_get_pixel_from_texture");
 	RESOLVE(blit_, OakBackendBlitFn, "oak_renderer_blit");
+	RESOLVE(attach_output_texture_, OakBackendAttachOutputTextureFn,
+			"oak_renderer_attach_output_texture");
+	RESOLVE(detach_output_texture_, OakBackendDetachOutputTextureFn,
+			"oak_renderer_detach_output_texture");
 	RESOLVE(opengl_context_, OakBackendOpenGLContextFn,
 			"oak_renderer_opengl_context");
 #undef RESOLVE
@@ -184,6 +190,8 @@ void DynamicRenderer::ResetFunctions()
 	flush_ = nullptr;
 	get_pixel_from_texture_ = nullptr;
 	blit_ = nullptr;
+	attach_output_texture_ = nullptr;
+	detach_output_texture_ = nullptr;
 	opengl_context_ = nullptr;
 }
 
@@ -271,6 +279,11 @@ QOpenGLContext *DynamicRenderer::OpenGLContext() const
 		: nullptr;
 }
 
+bool DynamicRenderer::IsOpenGL() const
+{
+	return backend_ == QStringLiteral("opengl");
+}
+
 void DynamicRenderer::Blit(QVariant shader, AcceleratedJob &job,
 					   Texture *destination, VideoParams destination_params,
 					   bool clear_destination)
@@ -301,4 +314,19 @@ void DynamicRenderer::DestroyInternal()
 	}
 }
 
+void DynamicRenderer::AttachOutputTexture(Texture *texture)
+{
+	if (attach_output_texture_ && texture) {
+		QVariant id = texture->id();
+		attach_output_texture_(handle_, &id);
+	}
+}
+
+void DynamicRenderer::DetachOutputTexture()
+{
+	if (detach_output_texture_) {
+		detach_output_texture_(handle_);
+	}
+}
+
 }

app/render/backend/dynamicrenderer.h

@@ -44,6 +44,12 @@ public:
 								  const QPointF &pt) override;
 	virtual QOpenGLContext *OpenGLContext() const override;
 
+	virtual bool IsOpenGL() const override;
+
+	virtual void AttachOutputTexture(Texture *texture) override;
+
+	virtual void DetachOutputTexture() override;
+
 protected:
 	virtual void Blit(QVariant shader, AcceleratedJob &job,
 				  Texture *destination, VideoParams destination_params,
@@ -84,6 +90,8 @@ private:
 	OakBackendFlushFn flush_ = nullptr;
 	OakBackendGetPixelFromTextureFn get_pixel_from_texture_ = nullptr;
 	OakBackendBlitFn blit_ = nullptr;
+	OakBackendAttachOutputTextureFn attach_output_texture_ = nullptr;
+	OakBackendDetachOutputTextureFn detach_output_texture_ = nullptr;
 	OakBackendOpenGLContextFn opengl_context_ = nullptr;
 };
 

app/render/backend/renderbackend_c.h

@@ -27,7 +27,9 @@ enum OakRenderBackendCapability {
 	OAK_RENDER_BACKEND_CAP_SHADERS = 1ULL << 1,
 	OAK_RENDER_BACKEND_CAP_BLIT = 1ULL << 2,
 	OAK_RENDER_BACKEND_CAP_READBACK = 1ULL << 3,
-	OAK_RENDER_BACKEND_CAP_VIEWER_CONTEXT = 1ULL << 4
+	OAK_RENDER_BACKEND_CAP_VIEWER_CONTEXT = 1ULL << 4,
+	OAK_RENDER_BACKEND_CAP_INSTANCE = 1ULL << 5,
+	OAK_RENDER_BACKEND_CAP_DEVICE = 1ULL << 6
 };
 
 struct OakRenderBackendInfo {
@@ -81,6 +83,9 @@ typedef void (*OakBackendBlitFn)(OakRenderBackendHandle handle,
 								 void *destination,
 								 const void *destination_params,
 								 bool clear_destination);
+typedef void (*OakBackendAttachOutputTextureFn)(OakRenderBackendHandle handle,
+											const void *texture_id);
+typedef void (*OakBackendDetachOutputTextureFn)(OakRenderBackendHandle handle);
 typedef void *(*OakBackendOpenGLContextFn)(OakRenderBackendHandle handle);
 
 #ifdef __cplusplus