nav, physics: Recast's and Detour's memory counted (nav_heap_bytes / _peak / _allocs, a counted allocator registered at load, tile bytes staged from it); package tests that crossing the map and back holds the native bytes

The user's walk showed the footprint rising outside the Ludic heap. Jolt's bytes were already counted;
the navmesh's were not, so nothing could see them. Now:
- ludic.nav nav_heap_test: fifty crossings of a four-tile map by the resident index hold the tiles in and
  the native bytes to the first crossing's; a thousand crowd walkers in and out grow nothing; a reset
  gives back every byte the mesh took.
- ludic.physics cross_heap_test: a 1 km map of 64 m chunks kept to a ring round a player crossing
  corner to corner and back, each chunk a heightfield, twelve owned posts and six owned scaled hulls
  as the game makes them: six more crossings hold the bodies, the shapes and Jolt's bytes and peak
  exactly. (A post made as an offset of a cylinder, with only the offset owned, leaked the cylinder
  every time: the game's solid_pillar owns its cylinder directly.)

lib/macos-arm64 rebuilt; lib/windows-x64 needs native/build.sh run on the PC for the new exports.

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

packages/ludic.nav/native/shim/nav_tiles.inl

@@ -103,10 +103,11 @@ NAV_SHIM void *nav_load(const unsigned char *buf, int size) {
 
 // a file read straight into the shim's own memory rather than a Ludic slice (which is never given
 // back): nav_stage hands out the room, nav_load_staged parses it and frees it, whatever the outcome
-NAV_SHIM void nav_unstage(unsigned char *buf) { free(buf); }
-NAV_SHIM unsigned char *nav_stage(int size) { return size > 0 ? static_cast<unsigned char *>(malloc(size)) : nullptr; }
+// staged from Detour's own (counted) allocator, since a tile's bytes are handed to it to free
+NAV_SHIM void nav_unstage(unsigned char *buf) { dtFree(buf); }
+NAV_SHIM unsigned char *nav_stage(int size) { return size > 0 ? static_cast<unsigned char *>(dtAlloc(size, DT_ALLOC_PERM)) : nullptr; }
 NAV_SHIM void *nav_load_staged(unsigned char *buf, int size) {
   void *h = buf ? nav_load(buf, size) : nullptr;
-  free(buf);
+  dtFree(buf);
   return h;
 }