[BUG] install.sh suggests bash-style PATH export for fish shell

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When installing Claude Code via the official install.sh script, the post-installation message suggests adding ~/.local/bin to PATH using a bash-style export command, even when the user is using fish shell.

The suggested command appends the following line to ~/.config/fish/config.fish:

export PATH="$HOME/.local/bin:$PATH"
````

This is not idiomatic or recommended in fish shell.

### What Should Happen?

For fish shell users, the installer should provide fish-appropriate guidance for updating `PATH`, such as using `fish_add_path`:

```fish
fish_add_path ~/.local/bin

This method:

• avoids duplicate PATH entries
• persists correctly across sessions
• aligns with fish shell design and best practices

Ideally, the installer would detect fish explicitly or show shell-specific instructions based on the user's environment.

Error Messages/Logs

Steps to Reproduce

1. Use fish shell
2. Run the official install script:

``sh
curl -fsSL https://claude.ai/install.sh | sh
``

1. Observe the post-installation output
2. Note that the suggested PATH modification for fish uses export PATH=...

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.15

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

• Shell: fish
• Installation method: install.sh
• Installation location: ~/.local/bin/claude (symlink to a versioned directory)

The installation location and symlink strategy itself work well; the issue is limited to the shell-specific PATH configuration guidance.