Feat/windows native support

[drtrafego]

Native Windows Support

This PR adds native Windows 10/11 support to Parallel Code without requiring WSL or WSL2.

What was added

• Native Windows support using ConPTY / node-pty
• Claude Code support on Windows (claude.cmd)
• Codex CLI support on Windows (codex.cmd / .exe)
• Antigravity CLI support (agy.exe)
• Windows PATH / PATHEXT command resolution
• Windows-compatible Git worktrees
• Directory junction support for shared dependencies
• Native Windows process-tree cleanup
• PowerShell support for Claude hooks
• AI Arena support on Windows
• Antigravity preset in AI Arena
• NSIS Windows installer
• windows-latest GitHub Actions CI
• Windows-specific automated tests
• Support for Windows paths, spaces and special characters
• Rebased onto latest upstream main

Testing

Windows-specific test suite passes locally:

• 57/57 tests passing
• Claude, Codex and Antigravity executable resolution tested
• ConPTY tested with .cmd shims
• Paths with spaces tested
• Special characters and accented characters tested
• Windows installer build tested

Build

The Windows build can be generated with:

npm run build:win

Output:

release/Parallel-Code-Windows-x64-Setup.exe

Related issue

Related to #9