Governance PoC Canonical Storage MUST (doc coherence)

[flyingrobots]

Title
Governance PoC Canonical Storage MUST (doc coherence)

Goal
Confirm ADR‑0003 and SPEC both mandate canonical PoC storage and update any remaining references.

Acceptance Criteria

• ADR‑0003 and SPEC both say MUST for canonical PoC envelope storage at refs/gatos/audit/proofs/governance/<proposal-id>.
• Link cross-check passes in docs CI.

Status

• Initial change landed in the ADR; verify cross-doc coherence.