get_network_request: improve get selected request description

[sebastianbenz]

Is your feature request related to a problem? Please describe.

Gemini CLI doesn't seem to understand our tool description for getting the selected element.

This doesn't work in the latest gemini-cli:

 Explain the selected network request

✦ I need a reqid to explain a specific network request. Please provide the reqid of the request you'd like me to explain. If you want to see all requests, you can use list_network_requests().

But this works:

> Explain the network request selected in the DevTools UI

──────────────────────────────────────────────────╮
│ ✓  get_network_request (chrome-devtools MCP Server) {}                                                                                                                                                                                                                                                                                         │
│```

### Describe the solution you'd like

n/a

### Describe alternatives you've considered

n/a

### Additional context

_No response_