Admin mutation log and managed session traces added

Minor Changes

• a49b105: Auto-capture for the ~/.releases/work/ maintenance workspace (two independent mechanisms):
  • Admin-mutation log. When RELEASES_RUN_DIR is set, every releases admin … write appends one JSONL line ({timestamp, command, target, result}) to $RELEASES_RUN_DIR/mutations.jsonl. Logged at the api-client chokepoint; telemetry/heartbeat endpoints are excluded. Unset → no-op, and fully fail-open (a logging failure never breaks the write).
  • Managed-session traces. --trace-dir <dir> on onboard, source fetch --wait, and overview batch --wait writes the terminal session/workflow as <dir>/<id>/{trace.json,summary.md}; admin discovery task get <id> --save [dir] snapshots an existing session retroactively. Trace dir precedence: explicit flag > RELEASES_RUN_DIR > ~/.releases/work/runs. summary.md mirrors the run-summary template in the monorepo's docs/architecture/maintenance-workspace.md.