False 'Update available!' banner when already on latest version

Description

The CLI displays an "Update available! Run: brew upgrade claude-code" banner even when the user is already on the latest version.

Steps to Reproduce

1. Have Claude Code installed via Homebrew
2. Observe the "Update available! Run: brew upgrade claude-code" banner at the bottom of the CLI
3. Run brew upgrade claude-code
4. Homebrew reports already on latest version
5. Banner persists

Environment

• Claude Code version: 2.1.5
• Homebrew version: 2.1.5 (latest available)
• Platform: macOS Darwin 25.1.0
• Install method: Homebrew

Expected Behavior

The "Update available!" banner should not appear when the installed version matches the latest available version.

Actual Behavior

Banner displays persistently despite being on the latest version (2.1.5).