Implement SIM-MUS Adapter v0.1

[bkr1297-RIO]

Purpose: add a small adapter above the existing receipt engine so SIM-001 Crossing Packets can be mapped into receipt-protocol inputs without changing the proof core.

Scope:

1. Map CrossingPacket to receipt intent.
2. Map SourcePoint/RIO approval to receipt approval.
3. Map Sentinel-verified surface to execution input.
4. Map SIM/RIO decisions to current ALLOW/BLOCK receipt decisions.
5. Return receipt summary to SourcePoint.

Initial tests:

• approved exact operation returns ALLOW
• drifted operation returns BLOCK
• draft-only crossing returns ALLOW
• draft with memory/action mutation returns BLOCK

Non-goals:

• Do not rewrite the receipt protocol.
• Do not expand decision vocabulary until implemented and tested.
• Do not make the receipt backend an authority source.

Keeper: SIM classifies the crossing. RIO decides admissibility. Sentinel verifies fidelity. MUS receipts the return. The adapter maps the crossing into proof.