Brings the MEM checkpoint up to the 2026-06-11 sessions: the std.sx pure-re-export facade arc (49a36bb/c75cd9c + issues 0120-0122), the allocator primitive rename (88bae3c), opt-in UFCS (a47ea14), Phase 2.2 typed helpers (84e0fb0), BufAlloc by-value init (51194a2); next step Phase 2.3 diagnostic wrappers. Older 2026-05-25-era records fold into collapsed details blocks.