MuseHub workspace — staging push + attestation smoke (KD-STAGING).

Model: Operator + Auto (Tier 3 push requires operator authorization).

Goal: Push gabriel-muse (KD-5b MCP) and musehub (KD-6b vault UI) to staging;
run KD-7 attestation smoke on a knowtation-domain staging vault.

Read: docs/MUSEHUB-ROADMAP.md, docs/MUSEHUB-OVERSEER-HANDOVER.md

Tasks:
  1. Operator: authorize muse push staging for gabriel-muse feat/kd-6a (includes KD-5b).
  2. Deploy musehub KD-6b to staging environment.
  3. Attestation smoke on staging vault (--attest flag).
  4. Update governance docs; Muse commit on feature branches.