## Why
The trusted UI host needs the local credential's public metadata to complete backend registration. `userVerification/enroll` previously returned only `credentialId`.
## What changed
- Return `algorithm` and `publicKey` for newly created or reused credentials. The algorithm is `ecdsaP256Sha256X962`; the public key is unpadded base64url SPKI-DER.
- Keep both fields optional in the protocol for compatibility with older app-servers, while current servers populate both.
- Document caller-owned backend registration and revocation, including checking metadata, signing an enrollment challenge with `userVerification/verify`, matching credential IDs, and preserving the authenticated account throughout registration.
## Testing
Add protocol coverage for absent or null metadata and populated-response round trips. Add an RPC assertion for enrollment metadata and extend the local enrollment test to check metadata when creating and reusing a key.
GitOrigin-RevId: f0726e8c430e27559e1a01ba2ea635993cbeba09
## Why
The existing `userVerification/*` handlers always returned unavailability, leaving local clients unable to use the native verification provider.
## What changed
- Dispatch status, enrollment, deletion, and challenge signing through an account-scoped provider. Enrollment creates or reuses a local key; it does not register credentials with a server.
- Restrict enrollment, deletion, and signing to stdio and in-process connections, rejecting WebSocket and remote-control callers before parameter validation.
- Bound native work to one operation per service with a 120-second timeout, and propagate in-process caller cancellation. Recheck connection, cancellation, and authentication state before delivering results, including after waiting for response queue capacity.
- Add device-gated verification capability wiring for the experimental in-process `codex-tui` client, with automatic activation still disabled by default.
## Testing
Add tests for local key reuse and deletion, decoded challenge signing, cancellation, authentication changes during verification and response queuing, concurrent worker rejection, and stdio/WebSocket RPC behavior.
GitOrigin-RevId: 7eac15a5ffb049d27bf8fedcfbae19a49a3f6a3d
riley-oai