CLI shows 'update available' when already on latest Homebrew cask version

Description

The Claude Code CLI (v2.1.86, installed via Homebrew cask) displays an "update available" banner prompting the user to run brew upgrade claude-code. However, running both brew upgrade --cask claude-code and brew upgrade claude-code report that the latest version is already installed.

Steps to reproduce

1. Install claude-code via Homebrew cask (currently v2.1.86)
2. Run claude — observe "update available" banner
3. Run brew update && brew upgrade --cask claude-code
4. Homebrew reports: "Warning: Not upgrading claude-code, the latest version is already installed"

Expected behavior

The update banner should not appear if the installed version matches the latest available version.

Environment

• macOS (Darwin 25.4.0)
• Homebrew, up to date
• claude-code cask v2.1.86