Better npm Global Installation Detection

What: Enhanced detection of npm global installations using npm config get prefix.

Details:

• Adds synchronous npm config get prefix command execution as a fallback
• Detects npm installations in custom prefix locations
• More reliable than hardcoded path matching alone
• Handles non-standard npm configurations
• Improves accuracy of installation type reporting and upgrade suggestions
• Evidence: G$() function at line 375878, specifically lines 375897-375898