## Why
OAuth discovery failures do not establish that an MCP server lacks OAuth
support. Reporting those failures as `unsupported` conflates an inconclusive
check with a confirmed result.
## What changed
- Add an `unknown` MCP authentication status across the protocol, app server,
CLI, and TUI.
- Preserve OAuth discovery errors so callers can report `unknown`, while
retaining `unsupported` for servers known not to support OAuth.
- Document the distinction in the app server API.
## Testing
- Verify transient HTTP discovery errors are preserved.
- Verify `codex mcp list --json` reports `unknown` when discovery is rate
limited.
GitOrigin-RevId: e4562985971606740538e542ec7eeee502111964