owned fields (25.5e): @owns(Kind) on a record's field, and owned_leaks

A field marked @owns(PhysShape) holds a handle its record owns. A function that releases one owned
field of a record (body_free(w, s.body)) and neither releases nor hands on another owned field of
the same record type (s.shape) gives the first back and loses the second - the phys_remove bug, at
compile time. ludic deps --resources (or --owned) lists them; owned_leaks is a number --check
ratchets. A test: the function that frees a solid's body alone is the one found; the one that frees
both is not.

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

selfhost/backend/emit_frame.ludic

@@ -229,6 +229,7 @@ function deps_keeps(f: pointer, seen: []bool) -> void {
   if g_arena_strict and n > 0 { exit(1) }
   deps_births(f, seen)
   deps_resources(f)                                # 25.5e
+  deps_owned(f)
 }
 
 function fr_consumed(n: Node) -> bool {