[FEATURE] [0.0.4-alpha] Add Session Merge Capability for Import

### Project
cortex-cli

### Description
Option to merge imported session with existing rather than replacing.

### Use Case
```bash
$ cortex <command>
error: feature not available
```

### Proposed Solution
1. Implement the suggested feature

### Alternatives Considered
_No response_

### Impact
All users

### Additional Context
_No response_