test(taproot): require physical signing confirmations

[BitHighlander]

Problem

Physical testing of the exact v7.15.0-rc23 full firmware artifact returned a valid 64-byte P2TR Schnorr signature without showing either transaction confirmation on the KeepKey. A P2WPKH control transaction on the same device and transport did require physical approval.

The deterministic P2TR vector checked only the signature bytes, so it could pass without asserting the security-critical button policy.

Change

Pin the complete expected response sequence for the real P2TR-input vector. The device must emit ButtonRequest_ConfirmOutput and then ButtonRequest_SignTx before phase-2 input/output requests and Schnorr signing.

This is a test-only change; it does not alter the wire schema or device protocol.

Verification

• python3 -m py_compile tests/test_msg_signtx_taproot.py
• git diff --check
• Full emulator/integration execution is performed by the firmware PR after pinning this exact SHA.

Hardware evidence

• Candidate: v7.15.0-rc23, full artifact SHA-256 92b292eb460c462df9084131a67a78f24fd4061b6d11822401dddd47c07c967f
• P2TR: valid serialization and 64-byte signature, no physical transaction confirmation
• P2WPKH control: recipient and fee were displayed and physically approved

This PR is intentionally draft until the paired firmware fail-closed guard and exact-head integration run are green.