Enhance file selection (skim) functionality in Amazon Q CLI

### Checks

- [x] I have searched [github.com/aws/amazon-q-developer-cli/issues](https://github.com/aws/amazon-q-developer-cli/issues?q=) and there are no duplicates of my issue
- [x] I have run `q doctor` in the affected terminal session
- [x] I have run `q restart` and replicated the issue again

### Operating system

Linux 5.10.235-208.919.amzn2int.x86_64 - Amazon Linux 2

### Expected behaviour

Nice work on skim, it's very useful! A couple of possible improvements:

1. When the prompt already contains `/context add` and Ctrl+K is pressed, the file selector should open directly without requiring an empty prompt.
2. Alternatively, allow binding the file selector to a different hotkey (preferably supporting alt hotkeys) to enable referencing files as part of a prompt rather than adding them to context.

cc @bergjaak

### Actual behaviour

Currently, the skim selection feature (Ctrl+K) only works from an empty prompt. When users want to reference a file as part of a prompt (as opposed to adding it to context), they need to type `/context add` first and cannot directly open the file selector with Ctrl+K if text is already in the prompt.

```
[chat-transcript]
> /issue

I'd be happy to help you report an issue or make a feature request. There are a few ways we can do this depending on what you're looking to report:

1. For issues with Amazon Q itself, we can use the `report_issue` tool to create a GitHub issue
2. For issues with the MagnolioAntBuildLogic package you're currently in, we could create a SIM issue
3. For feature requests related to any of the packages in your workspace, we can also use SIM

Could you please provide more details about:
1. What issue or feature request you'd like to report
2. Which system or package it relates to
3. Any specific details about the problem or requested feature

Once I have this information, I can help you create the appropriate report with all the necessary details.
[Tool uses: none]

> Let's report a github feature request for Q. The skim selection feature is really useful. However, it only works from an empty prompt. I don't actually need help typing `/context add` here. It would be nice if ctrl-k when the existing prompt is `/context add\s*` would open the file selector directly. Alternately, possibly a better feature would be the ability to just bind the file selector to a different hotkey (preferrably alt hotkeys would be supported) directly. There are situations when I want to reference a file as part of a prompt, as opposed to adding it to context

I'll help you report this feature request for Amazon Q. Let me create a GitHub issue with your suggestions for improving the file selection functionality.
[Tool uses: report_issue]
```

### Steps to reproduce

1. Start typing `/context add` in the Amazon Q CLI
2. Press Ctrl+K
3. Notice that the file selector doesn't open directly

### Environment

```yaml
(redacted)
```