feat(core,tui,app-server) personality migration (#10307)

## Summary
Keep existing users on Pragmatic, to preserve behavior while new users
default to Friendly

## Testing
- [x] Tested locally
- [x] add integration tests

codex-rs/core/tests/suite/mod.rs

@@ -49,6 +49,7 @@ mod otel;
 mod pending_input;
 mod permissions_messages;
 mod personality;
+mod personality_migration;
 mod prompt_caching;
 mod quota_exceeded;
 mod read_file;