False 'Update available' notification when installed via apt

Description

When Claude Code is installed via apt, the built-in update checker incorrectly shows an "Update available!" notification even when the package is already at the newest version.

## Steps to reproduce

1. Install Claude Code via apt
2. Run claude
3. Observe "Update available!" banner

## Expected behaviour

No update notification when the installed version is current.

## Actual behaviour

The banner appears even after running sudo apt update && sudo apt install --only-upgrade claude-code, which confirms the package is already at the newest version.

## Root cause (suspected)

The update checker compares against the npm registry version string (e.g. 2.1.126) but the apt package appends a Debian revision suffix (2.1.126-1). The string comparison
treats the apt version as older than the npm version.

## Environment

• Claude Code version: 2.1.126-1
• Installation method: apt
• OS: Linux (Ubuntu/Debian)