[client] transport: introduce pluggable frame transports

Move shared-memory ownership, LGMP session handling, queue access, and
DMA setup behind a transport interface. The LGMP backend preserves the
existing zero-copy frame and DMA paths while owning its lgmp:* options.

Expose the initialized EGL context through a versioned renderer interop
record for future accelerated decode backends. Add an LGMP-independent,
deterministic test transport for graphics-pipeline validation.

client/renderers/EGL/cursor.h

@@ -44,7 +44,7 @@ bool egl_cursorSetShape(
     const uint8_t * data);
 
 void egl_cursorSetColorTransform(EGL_Cursor * cursor,
-    const KVMFRColorTransform * transform);
+    const LGColorTransform * transform);
 
 void egl_cursorSetSize(EGL_Cursor * cursor, const float x, const float y);