Windows Auto-update Fails with Incorrect Package Path Formatting

Bug Description
Title: Auto-update fails on Windows with incorrect path formatting

Description:
When running claude update on Windows, the auto-update mechanism fails with a path formatting error. The update
process incorrectly inserts backslashes into the npm package name.

Steps to reproduce:

1. Run claude update on Windows when an update is available
2. Update check succeeds and finds new version
3. Installation fails with "Warning: Could not determine installation type"
4. Error message suggests incorrect command with backslashes in package name

Expected behavior:
Auto-update should complete successfully without manual intervention

Actual behavior:
Update fails and suggests invalid npm command:
npm update @node_modules\@anthropic-ai\claude-code\

Workaround:
Manual update works correctly:
cd ~/.claude/local && npm update @anthropic-ai/claude-code

Environment:

• OS: Windows (MINGW64_NT-10.0-26100)
• Claude Code version: 1.0.58 (updating to 1.0.59)
• Installation type: Local (~/.claude/local)

Root cause:
The update mechanism appears to have a Windows-specific bug where forward slashes in the npm package name are
incorrectly converted to backslashes, making the suggested command invalid.

-Made with Claude

Environment Info

• Platform: win32
• Terminal: windows-terminal
• Version: 1.0.59
• Feedback ID:

Errors

[{"error":"Error: Language not supported while highlighting code, falling back to markdown: \n    at hJ (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:1184)\n    at file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:2172\n    at Array.map (<anonymous>)\n    at hJ (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:2143)\n    at file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:2059\n    at Array.map (<anonymous>)\n    at hJ (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:2048)\n    at file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:912\n    at Array.map (<anonymous>)\n    at $V (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:903)","timestamp":"2025-07-23T22:31:16.843Z"},{"error":"Error: Language not supported while highlighting code, falling back to markdown: \n    at hJ (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:1184)\n    at file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:2172\n    at Array.map (<anonymous>)\n    at hJ (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:2143)\n    at file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:2059\n    at Array.map (<anonymous>)\n    at hJ (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:2048)\n    at file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:912\n    at Array.map (<anonymous>)\n    at $V (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:903)","timestamp":"2025-07-23T22:31:16.854Z"},{"error":"Error: Language not supported while highlighting code, falling back to markdown: \n    at hJ (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:1184)\n    at file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:912\n    at Array.map (<anonymous>)\n    at $V (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:903)\n    at K_B (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:2417:8747)\n    at RM (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:65:19859)\n    at Tv (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:67:42847)\n    at Rv (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:67:38368)\n    at YS (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:67:38296)\n    at lM (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:67:38150)","timestamp":"2025-07-23T22:32:38.125Z"},{"error":"Error: Language not supported while highlighting code, falling back to markdown: \n    at hJ (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:1184)\n    at file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:912\n    at Array.map (<anonymous>)\n    at $V (file:///C:/Users/frank/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1491:903)\n    at K_B (file:///C:/Us

Note: Error logs were truncated.