Update notification always shown for winget installations due to npm version check

Description

When Claude Code is installed via winget (Anthropic.ClaudeCode), the "Update available!" notification is effectively permanent, because the update check compares against the latest npm version.

Problem

• npm releases are always ahead of winget releases (winget packaging/review takes additional time)
• By the time winget catches up to version N, npm is already at N+1 or N+2
• This means winget users always see the yellow "Update available! Run: winget upgrade Anthropic.ClaudeCode" banner
• Running winget upgrade reports "No applicable update found" since the latest winget version IS already installed

Steps to Reproduce

1. Install Claude Code via winget install Anthropic.ClaudeCode
2. Launch claude
3. Observe "Update available!" notification at the bottom
4. Run winget upgrade Anthropic.ClaudeCode → "No applicable update found"
5. Notification persists indefinitely

Current behavior

• Installed (winget): 2.1.70
• Latest (npm): 2.1.72
• winget upgrade → no update available
• Notification still shows

Expected behavior

The update check should be aware of the installation method and compare against the correct package registry:

• npm install → check npm registry
• winget install → check winget registry (or suppress if winget version matches latest winget release)

Environment

• OS: Windows 11 Pro
• Claude Code: 2.1.70 (installed via winget)
• Node.js: v22.22.0