What's new
- [new] Added a dedicated migration subsystem for external agent configuration, including flow and model handling in the TUI.
- [changed] Updated SandboxPolicyDeserialize variants to separate WorkspaceWrite and read-only ExternalSandbox cases.
- [changed] Restructured ServerRequest and ThreadItem variants to better represent permission approvals and review actions.
Under the hood
- Introduced four new source modules under tui/src for external agent config migration.
- Added a new typed payload TUIexternalAgentConfig to support the migration path.
- Adjusted internal enums for GuardianApprovalReviewAction and UserInput to reflect updated connector and image handling shapes.