feat(render3d): Vulkan in a macOS window through MoltenVK; window built-ins take a slice's elements; the NEAR_FADE SPIR-V

- a CAMetalLayer on the view (cocoa.ll win_metal_layer), VK_EXT_metal_surface, QuartzCore linked
  with Vk.*; the drawable measured after the layer sets the backing scale
- vk_mac.ll opens MoltenVK directly after any loader: a bundle ships only libMoltenVK.dylib
- a covered window is not presented to (win_visible); one frame in flight on macOS
  (R3D_VK_INFLIGHT), with images, buffers and descriptor pools held until it is done
- win_held / win_mouse / win_pad / win_touch / win_text / win_present pass slice elements (arg_buf):
  every windowed program died on its first input poll
- variants.list and SPIR-V for the three NEAR_FADE foliage programs

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

packages/ludic.render3d/env.ludic

@@ -199,6 +199,10 @@ export state Render3dState {
   gvk_al_spare: []int = null        # ids to reuse
   gvk_pool: long = 0
   gvk_fence: bytes = null
+  gvk_frame_fence: bytes = null     # the presented frame still on the GPU (one frame in flight)
+  gvk_frame_pending: bool = false
+  gvk_frame_pending_cb: pointer = null
+  gvk_inflight: int = -1            # -1 until asked: 1 leaves the presented frame in flight
   gvk_has_hqr: bool = false
   gvk_ts_period: float = 0.0             # float bits: nanoseconds per timestamp tick
   gvk_qpool: long = 0