## Why
User-verification cancellations previously discarded failure reasons, leaving MCP servers unable to distinguish user cancellation from unavailable approval, interruption, or invalid proof.
## What changed
- Carry a bounded `openai/userVerificationReason` value in response `_meta` for verification failures, declines, and cancellations across the TUI, app server, and MCP client.
- Preserve recognized reasons and classify invalid responses, missing or invalid proofs, response errors, closed response channels, interruptions, and unavailable approval.
- Discard unknown reasons and unrelated metadata. Keep proof material out of decline and cancellation responses, and keep display messages and raw error diagnostics out of response metadata.
## Testing
Add and update tests for typed failure propagation, metadata filtering, invalid proofs, response-channel failures, interrupted requests, and unavailable approval, including TUI RPC and native MCP response coverage.
GitOrigin-RevId: 6b7f855ce8eb13e759b5b86d0dc2b1afdfcff7b3
berkdeniz-oai
b38942ce7c