NemoClaw Upgrade Issue: Existing Agents Removed After Update

### Investigation Summary

During the NemoClaw version upgrade process, it was observed that all existing agents were removed after the update was completed
(base) aic@master-1:~$ nemoclaw update --check
Current NemoClaw version: 0.0.88
Latest maintained version: 0.0.90

### Description

During testing of the NemoClaw version upgrade process, it was observed that all existing agents were removed after the update was completed. Users are required to manually recreate their agents and reconfigure settings, which can lead to workflow disruptions and additional effort. The expected behavior is that agent data and configurations should be preserved during upgrades to ensure a seamless transition between versions. Further investigation is needed to determine why agent information is not being retained and to implement a proper migration or backup mechanism.

### Reproduction Steps

(base) aic@master-1:~$ nemoclaw update --check
Current NemoClaw version: 0.0.88
Latest maintained version: 0.0.90
Install type: installer-managed clone
Update available: yes
Maintained update path: curl -fsSL https://www.nvidia.com/nemoclaw.sh | bash
(base) aic@master-1:~$ nemoclaw update
Current NemoClaw version: 0.0.88
Latest maintained version: 0.0.90
Install type: installer-managed clone
Update available: yes
Maintained update path: curl -fsSL https://www.nvidia.com/nemoclaw.sh | bash
Run the maintained NemoClaw installer now? [y/N]: y

(base) aic@master-1:~$ nemoclaw --version
nemoclaw v0.0.90

### Environment

Operating System: Ubuntu 25.10
Kernel: Linux 6.17.0-40-generic
Architecture: x86-64
node --version: v24.16.0
docker --version: Docker version 28.2.2, build 28.2.2-0ubuntu1
nemoclaw --version: nemoclaw v0.0.90

### Debug Output

no output

### Logs

```shell

```

### Checklist

- [x] I confirmed this bug is reproducible
- [x] I searched existing issues and this is not a duplicate

Reproduce the upgrade with `nemoclaw update --check` and `nemoclaw update`, moving from v0.0.88 to v0.0.90 as shown. Trace the installer-managed upgrade to determine why existing agents and settings disappear; done means an upgrade preserves them or provides a reliable migration or backup path without manual recreation.

Written by the indexing model from the issue text.