Release menhera-loop v0.5.1

Post-release fixes for the two P1s confirmed in the v0.5.0 review:
the ledger's failure-text fallback now applies only to verification
commands (read-only greps stay unknown, silent-recovery stays quiet),
and ko/ja request suffixes/fillers no longer over-block requirement
evidence. Plus gate-precision cleanups: python -m pytest / deno test
recognition, last-message-only completion claims, negated failure
text, read-only-first ledger eviction, shared path-kind classifier.