render3d: @owns on the handles records hold

Target's framebuffer and its colour and depth textures, a Mesh's index buffer (gvk_buf_new /
gvk_buf_delete now @creates / @releases GpuBuffer too), a Prim's mesh and an Actor's own skin clone.
ludic deps --resources over main: resource_drops 0, owned_leaks 0; a probe freeing a Target's fbo
alone was reported for its colour and depth (2), then removed. Compiled (steady).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/ludic.render3d/mesh.ludic

@@ -7,7 +7,7 @@
 property Mesh {
   vao:   int = 0,            # OpenGL's vertex array object (gpu.ludic's, on that backend)
   vbo:   int = 0,            # the first vertex buffer
-  ebo:   int = 0,
+  @owns(GpuBuffer) ebo:   int = 0,
   count: int = 0,            # indices (ebo != 0) or vertices
   mode:  int = 4,            # GL_TRIANGLES
   itype: int = 0x1405,       # GL_UNSIGNED_INT