rubyperf evidence

Each rule has a claim file and measured JSONL from examples/bench/evidence_rb.rb:

• rb-string-plus-hot — .md + .jsonl
• rb-array-plus-rebind — .md + .jsonl
• rb-puts-hot — .md + .jsonl
• rb-hash-merge-in-loop was removed; see _removed/

rb-regexp-new-hot and rb-json-hot have JSONL and stay hint. rb-date-parse-in-loop was removed; see _removed/.

Defaults and the escalation rule: ../docs/evidence-policy.md and root docs/rule-regression.md.