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/videoparams.cpp

@@ -29,6 +29,7 @@ extern "C" {
 #include <QtMath>
 
 #include "core.h"
+#include "ofxImageEffect.h"
 
 namespace olive
 {
@@ -120,6 +121,17 @@ VideoParams::VideoParams(int width, int height, int depth, PixelFormat format,
 	set_defaults_for_footage();
 }
 
+void VideoParams::set_channel_count(const std::string &ofxComponent)
+{
+	if (ofxComponent == kOfxImageComponentAlpha) {
+		channel_count_ = 1;
+	} else if (ofxComponent == kOfxImageComponentRGB) {
+		channel_count_ = kRGBChannelCount;
+	} else if (ofxComponent == kOfxImageComponentRGBA) {
+		channel_count_ = kRGBAChannelCount;
+	}
+}
+
 VideoParams::VideoParams(int width, int height, const rational &time_base,
 						 PixelFormat format, int nb_channels,
 						 const rational &pixel_aspect_ratio,