feat(platform): 插件协议系统 - 支持声明式渠道、工作流与参考媒体映射

backend/internal/protocol/builtin.go

@@ -84,6 +84,21 @@ func Builtins() *Registry {
 	return registry
 }
 
+// BundledManifest returns the canonical unified manifest for a declarative
+// bundled contribution. Host-backed builtins are generated by the installer
+// because their execution engine lives in the application binary.
+func BundledManifest(id string) (Manifest, bool) {
+	adapter, ok := Builtins().Get(id)
+	if !ok {
+		return Manifest{}, false
+	}
+	manifest, ok := adapter.(manifestAdapter)
+	if !ok {
+		return Manifest{}, false
+	}
+	return manifest.manifest, true
+}
+
 func allSurfaces() []Surface {
 	return []Surface{SurfaceAdminSystemChannel, SurfaceUserCustomChannel, SurfaceCanvas, SurfaceCreation, SurfaceAgent}
 }