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>

changes/vulkan-leaks.md

@@ -0,0 +1,15 @@
+bump: patch
+type: fix
+**The Vulkan renderer no longer leaks memory 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 on
+every model loaded later); the pixels are now converted straight into the mapped staging buffer.
+The per-level and per-layer views made for mipmapped and layered targets outlived their texture,
+and on MoltenVK a view keeps its Metal texture alive, so every rebuild of the screen-sized targets
+left the last set in memory; a released texture now takes its views with it, and the cache is
+keyed by numbers rather than a string built on every call. The Vulkan structs filled for a draw, a
+pass, a barrier, a descriptor set or a buffer (about sixty call sites, several per draw) come from
+a reused 1 MB scratch ring instead of a malloc each; the descriptor-set cache and the retired
+buffer list are emptied and refilled rather than replaced; and on macOS the frame drains an
+autorelease pool (`Vk.frame_pool()`), which MoltenVK and the layer rely on. `R3D_VK_PROF` now
+also prints, every 120 frames, the Vulkan objects made and destroyed by kind and the length of
+every cache, so a kind made each frame and never destroyed shows at once.