Add runtime counters tracking FBIP reuse vs copy operations:
- lux_fbip_reuse_count: incremented when rc=1 allows in-place mutation
- lux_fbip_copy_count: incremented when rc>1 forces allocation
Output now shows both memory stats and FBIP stats:
[RC] No leaks: 13 allocs, 13 frees
[FBIP] 3 reuses, 0 copies
Rename test_no_fbip.lux to test_ownership_transfer.lux to better
reflect that ownership transfer enables FBIP even with aliases.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
