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.

CMakeLists.txt

@@ -104,6 +104,18 @@ endif()
 find_package(OpenGL REQUIRED)
 list(APPEND OLIVE_LIBRARIES OpenGL::GL)
 
+# Optional: Link Vulkan and shaderc (for the Vulkan render backend)
+find_package(Vulkan)
+find_package(PkgConfig)
+if(PkgConfig_FOUND)
+  pkg_check_modules(SHADERC shaderc)
+endif()
+if(Vulkan_FOUND)
+  message(STATUS "Vulkan found: ${Vulkan_LIBRARIES}")
+else()
+  message(STATUS "   Vulkan not found. The Vulkan render backend will be disabled.")
+endif()
+
 # Link OpenColorIO
 find_package(OpenColorIO 2.1.1 REQUIRED)
 list(APPEND OLIVE_LIBRARIES ${OCIO_LIBRARIES})