🔥 feat(cli): remove deprecated rag subcommands and migrate functionality

## Changes

### Removed Commands

- `3gpp-ai rag migrate` - Removed migration functionality entirely

- `3gpp-ai rag query` - Moved to `workspace query`

- `3gpp-ai rag status` - Moved to `workspace status`

### New Commands (under workspace)

- `3gpp-ai workspace query` - Query the LightRAG knowledge graph

- `3gpp-ai workspace status` - Show LightRAG configuration and status

### Files Modified

- `packages/3gpp-ai/threegpp_ai/cli.py`

  - Removed `rag_app` import and `app.add_typer(rag_app, name="rag")`

  - Added `workspace query` command

  - Added `workspace status` command

  - Added imports: `Annotated`, `QueryMode`, `StorageBackend`, `TDocRAG`

- `packages/3gpp-ai/threegpp_ai/lightrag/cli.py`

  - Removed migrate command

  - Removed migration imports

  - Marked module as deprecated

- `packages/3gpp-ai/threegpp_ai/lightrag/migration.py` - Deleted

### New CLI Structure

```

3gpp-ai --help

├── summarize   (existing)