Merge r3d/cb-cap into main (gathering every branch; main's side kept on conflicts)

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

packages/ludic.render3d/env.ludic

@@ -360,6 +360,8 @@ export state Render3dState {
   gvk_us_set: long = 0
   gvk_us_draw: long = 0
   gvk_n_draws: int = 0
+  gvk_cb_draws: int = 0            # draws recorded into the frame's command buffer so far
+  gvk_cb_cap: int = -1             # a command buffer is submitted after this many (0 = never; -1 unread)
   gvk_n_asked: int = 0              # draws that reached gvk_draw_now: every one the renderer asked for
   gvk_n_flush: int = 0
   gvk_prof_frames: int = 0