[FEATURE] Add Termius Support for `/terminal-setup` 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

The /terminal-setup command currently does not support Termius terminal emulator. When running the command in Termius, it shows:

Terminal setup cannot be run from Termius.

This command configures a convenient Shift+Enter shortcut for multi-line prompts.
Note: You can already use backslash ( + return to add newlines.

To set up the shortcut (optional):

1. Exit tmux/screen temporarily
2. Run /terminal-setup directly in one of these terminals:

• macOS: iTerm2, Apple Terminal
• IDE: VSCode, Cursor, Windsurf, Zed
• Other: Ghostty, WezTerm, Kitty, Alacritty, Warp

1. Return to tmux/screen - settings will persist

Proposed Solution

When running /terminal-setup, Termius should be:

1. Automatically detected if installed on the system
2. Listed as an available terminal option alongside VS Code, iTerm2, and WezTerm
3. Configured to support Shift+Enter for newlines in Claude Code prompts

Alternative Solutions

_No response_

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

_No response_

Additional Context

_No response_