[FEATURE] Add /version slash command

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Would be nice to be able to get the version from the app using a slash command, odd that I need to quit or allow permissions.

Proposed Solution

/version => 2.1.75

Alternative Solutions

I quit and used "claude -v" and asked in the app "What is your version number". Both work, but are steps away.

Priority

Low - Nice to have

Feature Category

CLI commands and flags

Use Case Example

I am submitting an issue the UI asks for the claude version. I then need to look go retrieve that.

Additional Context

<img width="1068" height="391" alt="Image" src="https://github.com/user-attachments/assets/dc736429-cfff-4005-bd30-4a909f0af81b" />