Feature Request: Support zsh as defaultShell for ! bang commands

Problem

Currently, Claude Code's settings.json only allows "defaultShell": "bash" or "powershell" for ! bang commands. On macOS (and many Linux setups), zsh is the default login shell, and users maintain all their aliases, PATH exports, plugins, and environment configurations in ~/.zshrc.

When using ! to run quick commands inside Claude Code, everything executes in bash, which:

1. Does not load ~/.zshrc.
2. Breaks user-defined aliases (e.g. alias ls="lsd").
3. Creates a confusing experience for anyone whose daily workflow is built around zsh.

Request

Please add "zsh" as a valid option for "defaultShell" in settings.json (and ideally auto-detect $SHELL on macOS).

Use case

As a heavy zsh user, I want ! commands to run inside zsh so that my environment, aliases, and completions work consistently without having to prefix every command with zsh -c \"...\".