## Why
Clients that complete an external agent config import outside the app server need a way to include the result in import history.
## What changed
- Add `externalAgentConfig/import/recordHistory` to persist completed item results and return a generated import ID.
- Store the optional provider ID for regular imports and expose it when reading import history.
- Update the generated JSON and TypeScript protocol schemas for the new request, response, and history field.
## Testing
- Cover recording and reading an externally completed import through the app-server protocol.
- Cover provider ID persistence and updates in the state runtime.
GitOrigin-RevId: 935401e899ec9eeb38f54c182e45a16642411deb
## What changed
- Move migration detection, import orchestration, models, and reporting from
`codex-app-server` into `codex-external-agent-migration`.
- Keep app-server protocol conversion in a dedicated boundary module.
- Organize source-specific configuration, sessions, hooks, plugins, commands,
subagents, and memory handling behind shared migration adapters.
- Relocate and split the migration tests alongside the extracted service.
GitOrigin-RevId: 3378ec2064806a28136d6ac98664ca1d75414a4e
charlesgong-openai