0c09093ef9
Records the diagnosis (18f.2 bencher finding -> tail-call drop elision in match arms whose body consumes pattern-binders into the tail-call), the new pre-tail-call seam in lower_match, the opt-in rc-stats counter test infrastructure (18g.0), the TDD record, and the end-to-end verification on bench_latency_explicit (11M -> 1M live cells; the 1M residue is the persistent Tree cache and queues as 18g.2).