New Flag Request: --confirm-send

### Describe the feature or problem you'd like to solve

Guard against accidental API calls.

### Proposed solution

I feel a strongly negative reaction when I accidentally hit enter in the Copilot CLI. This causes my prompt to send while I'm in the middle of writing it.

Besides human error, not all software uses the same style of Enter vs. Shift+Enter for sending vs. newlines. It can be difficult to context swap between programs which use different styles.

**Add a flag**: --confirm-send
**What it does**: The terminal displays: "Press enter again to send this prompt", or some variation. The user must press the enter key twice to send the prompt to Github Copilot.
**Why**: Prevent accidental waste of money and tokens. Reduce strain on Copilot servers.

### Example prompts or workflows

All workflows where a human is typing into the Copilot CLI.

### Additional context

_No response_