## Why
Allow MCP authentication to complete when the browser cannot reach the callback page by accepting the full redirect URL copied from its address bar.
## What changed
- Add `codex mcp login <name> --no-browser` to print the authorization URL and accept a pasted callback without launching a browser. HTTP callbacks remain supported while waiting for input.
- Validate pasted redirect URLs and OAuth responses before exchanging tokens, hide terminal input, bound input size, and avoid echoing callback values in diagnostics.
- Preserve manual input across discovered-scope retries and support cancellation during callback input and token exchange.
## Testing
Add unit and CLI integration tests for callback validation, bounded input, credential storage, HTTP callback completion with stdin open, scope retries, and cancellation during token exchange.
GitOrigin-RevId: 16ea9c3221f72d93e6e3e5acdc6b9465293a0a65
