[BUG] `opusplan` model alias missing from `/model` command list but works when specified

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?

The opusplan model alias is documented and fully functional, but it does NOT appear in the list when running /model without arguments. However, when you type /model opusplan directly, it works perfectly.

This creates a discoverability problem - users won't know opusplan exists unless they read the docs.

What Should Happen?

When running /model to see available options, opusplan should be displayed alongside opus, sonnet, haiku, etc.

According to the official docs, opusplan is fully supported:
> Special mode that uses opus during plan mode, then switches to sonnet for execution

Error Messages/Logs

Evidence

<img width="1056" height="472" alt="Image" src="https://github.com/user-attachments/assets/60c29aea-a94c-4510-bc53-e39232a64579" />

Steps to Reproduce

1. Run /model (without arguments)
2. Observe: opusplan is NOT in the list
3. Type /model opusplan directly
4. Result: Works perfectly

Expected: Step 2 should show opusplan in the list

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.0.67 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Cursor

Additional Information

Impact

Severity: Medium - Discoverability issue

Most users would benefit from the cost-efficient opusplan hybrid mode, but won't discover it because it's hidden from the menu.

### Root Cause

The /model command has two code paths:

• Display logic - Hardcoded list missing opusplan (buggy)
• Parser logic - Correctly recognizes opusplan (works)

### Suggested Fix

Update the /model display logic to include all documented model aliases.

### Additional Context

• Platform: macOS
• Claude Code: Latest
• Model: opusplan (missing from menu, works when typed)