Add launch flag to bypass trust folder prompt

When automating `copilot` CLI from scripts it would be very helpful to have a way to opt-in to trusting the folder via a launch flag so that the folder doesn't first have to be trusted via an interactive session and answering the prompt manually, or by directly editing the `~\.copilot\config.json` file.

I'm imagining something like:

```
$ copilot --trust-folder --allow-all-tools
```

Related #1121

Start at the copilot CLI's launch argument handling and read related issue #1121 for existing context. Add a launch flag that opts the current folder into trust without an interactive prompt, including when combined with --allow-all-tools. Done means scripted launches can trust the folder without editing config.json or answering prompts manually.

Written by the indexing model from the issue text.