nx_js_gc_gate.nx

nx_js_gc_gate.nx -- prove the non-moving mark-sweep collector (conservative word-scan made EXACT by the block-start bitmap). Under a TINY 64KB threshold (a collection fires ~every 500 objects): (A) RECLAIM -- 100k garbage objects leave resident memory BOUNDED (nx_pool_hp plateaus; collections fire). (B) RETAIN -- large structures kept live across many collections SURVIVE intact (missing root=crash/wrong). (C) EXACT -- every result stays V8-exact under aggressive GC, incl the 6 self-validating Octane benches. Any missing root manifests as a use-after-free the self-checking programs catch. expect_exit: 0 license_tier: ORIGINAL NOTE: helpers take <=2 data args -- nx_cc miscompiled a 3-arg helper call here (crash before/at the callee), so `want` is threaded through a module global instead of a 3rd parameter.