simplify pr-watch to USER-only (#517)
Retire the dual-agent AUDIT half of pr-watch now that the local audit agent is gone (plugin #512, vergil-tooling#1872). Keep the USER Monitor & reconcile loop (vrg-pr-await -> reconcile failing CI + human review -> push -> stop when green). Remove the AUDIT Review & gate half, the identity-keying / 'both agent sessions' framing, the vergil-audit/approved stop condition, and the per-commit-gate note. Update the README skills table, the Ship-a-change step, and the site skills index. vrg-audit-approve and the audit identity stay as dormant infrastructure; they are simply no longer invoked by a skill. Ref #516