fix(render3d): nothing allocated in the steady state - the Vulkan allocator reuses its records

gvk_mem_new made a one-slot []pointer per allocation, and turned the requirement's size and
alignment into strings to read them as ints; gvk_list_drop_last rebuilt the spare-record list to
drop its last entry; gvk_mem_id did the string round trip on every free. One slot is kept
(gvk_map_slot), int() truncates a long, the spare list pops. Every Text.to_int(string(x)) in
render3d is int(x) now.

Vk.heap_bytes() (vk_mac.ll: malloc_zone_statistics' size_in_use; 0 on Windows) and
examples/rendering/steady.ludic, in the suite: a buffer released and made again 5000 times and
600 whole frames gain 0 bytes each - the allocator before this, 1,120,000 over the 5000.

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

runtime/native/vk_win.ll

@@ -369,3 +369,9 @@ define void @lvk_frame_pool() {
 entry:
   ret void
 }
+
+; the heap's live bytes are asked for on the Mac only (vk_mac.ll); 0 here, and a test skips its check
+define i64 @lvk_heap_bytes() {
+entry:
+  ret i64 0
+}