## Why
Repository-scoped imports must not follow redirected Codex paths and write
generated configuration outside the repository.
## What changed
- Reject repository migration scopes when generated configuration paths are
symlinks or, on Windows, reparse points.
- Recheck hook and subagent destinations during import, skipping redirected
directories, files, and dangling links without reporting them as imported.
## Testing
Add service and app-server coverage for redirected generated destinations,
including a repository path replaced with a symlink after detection.
GitOrigin-RevId: 3afb521ead9d76250f0e967eccfdd1dc194f027a
## 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
jif