fence (25.1c): the census reads the heap outside Ludic's blocks; blocks counted at malloc's own size

The census's native line is malloc's live bytes over every zone since judging began less what
Ludic's tracked blocks kept - the libraries' and drivers' growth, read before the census file is
opened. A tracked block counts malloc_size(), not the size asked for, so kept is what the heap pays
and the residual carries no rounding. @malloc_zone_statistics is declared once, by the fence or by
Os.heap_bytes.

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

examples/lang/alloc_fence_leak.ludic

@@ -1,6 +1,6 @@
 # alloc_fence_leak.ludic - frame 50 keeps one record in a list that outlives it. The fence fails
 # the run there (exit 86) and names this file's `new Box` line; under R3D_ALLOC_FENCE=count it
-# runs on and prints `kept 72 bad 1` (the record and the list's first growth, one frame).
+# runs on and prints `kept 80 bad 1` (the record and the list's growth, at malloc's own sizes, in one frame).
 program AllocFenceLeak {
   property Box { a: int = 0, b: int = 0 }
   entry {