fix(render3d): the Vulkan renderer stops leaking as it loads and draws

- every texture upload malloc'd a CPU copy of its pixels and never freed it (236 MB over the
  valley's boot, and again for every model loaded later): the pixels are converted straight
  into the mapped staging buffer
- the per-level and per-layer views gvk_view_of made outlived their texture, and on MoltenVK a
  view keeps its Metal texture alive: a released texture takes its views with it, and the cache
  is keyed by numbers instead of a string built on every call
- the Vulkan structs filled for a draw, pass, barrier, descriptor set, buffer, allocation or
  upload (about sixty call sites) come from a reused 1 MB scratch ring (gvk_tmp)
- the descriptor-set cache and the retired buffers are emptied in place, not replaced; the grass
  cull's dispatch arguments are made once
- macOS drains an autorelease pool each frame (Vk.frame_pool, lvk_frame_pool in vk_mac.ll)
- R3D_VK_PROF reports Vulkan objects made and destroyed by kind, and every cache's length
- examples/rendering/smooth presents through render3d, so it runs on Vulkan too

The full valley on headless Vulkan loads to 2.18 GB and holds (it passed 8 GB while loading
before). ludic-dev test 305/305, selfhost-test 33/33.

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

runtime/native/vk.ludic

@@ -25,6 +25,9 @@ import "vk_api.ludic"
 # Vk.sl_active() says whether it was. Each Vk.sl_* is the sl* export of the same name and returns
 # its sl::Result (0 is eOk); -1 means there is no Streamline (macOS, or the DLL missing). The
 # structs are plain memory, laid out as the SDK headers (include/sl_*.h, SDK 2.14.1) declare them.
+# Once a frame: on macOS drains what MoltenVK and the layer autoreleased during the last one (a
+# program pumping its own events has no other pool); nothing elsewhere.
+extern function vk_frame_pool() = "lvk_frame_pool"
 extern function vk_sl_prefer(on: int) = "lvk_sl_prefer"
 extern function vk_sl_active() -> int = "lvk_sl_active"
 extern function vk_sl_init(pref: pointer, sdk_version: long) -> int = "lsl_slInit"