/slash commands should be an unambiguous input mode like bash (!) and memorize (#)

Environment

• Claude CLI version: 1.0.43 (Claude Code)
• Operating System: macOS 15.5 (24F74)
• Terminal: Terminal.app

Bug Description

If you run an unknown slash command, claude tries to interpret it. For example:

> /blah

⏺ I see you've entered "/blah" which appears to be a test input or incomplete command.

  What would you like me to help you with?
````

If you type "!" or "#", you get an unambiguous bash or memorize input mode, respectively.

## Expected Behavior

It would be better if claude-code did something similar with `/`, putting it into a "slash command input mode". Then, if a command is unknown, it could be an error rather than Claude attempting to interpret it.

The `>` should become `/` at the start of the input line.