feat: Add Windows WSL auto-detection and bridge mode

[PhenixStar]

Summary

• Auto-detect Windows (MINGW/MSYS/CYGWIN) in install.sh — no longer errors on Windows
• Install dependencies inside WSL automatically when Windows is detected
• Create Windows-side codex-agent shim at ~/bin/codex-agent with path conversion
• Add codex-agent-wsl.sh bridge wrapper handling 3 Windows path formats
• Fix Linux script command syntax in tmux.ts (macOS BSD vs Linux util-linux)
• Update README.md and SKILL.md with Windows/WSL documentation

How it works

1. install.sh detects Windows via uname -s (CYGWIN/MINGW/MSYS)
2. Checks WSL is available with a default distro (wsl --status)
3. Re-invokes itself inside WSL for tmux/bun/codex install
4. Creates ~/bin/codex-agent shim on Windows side
5. Shim auto-converts Windows paths to WSL /mnt/ format and routes through wsl -e bash

Changes

• scripts/install.sh: Added PLATFORM=windows detection, install_via_wsl(), create_windows_shim(), convert_to_wsl_path()
• scripts/codex-agent-wsl.sh: New WSL bridge wrapper with 3-format path conversion (Git Bash /c/, CMD C:\, PowerShell C:/)
• src/tmux.ts: Detect macOS vs Linux at runtime for script command syntax (script -q logfile cmd vs script -q -c "cmd" logfile)
• README.md: Added Windows/WSL installation section
• SKILL.md: Added Windows/WSL prerequisites note

Path conversion

The bridge converts -d/--dir and -f/--file flag values automatically:

• /c/Users/foo → /mnt/c/Users/foo (Git Bash)
• C:\Users\foo → /mnt/c/Users/foo (CMD)
• C:/Users/foo → /mnt/c/Users/foo (PowerShell)

CWD is also auto-converted so agents work in the correct directory.

Linux script fix

The script command in tmux.ts used macOS/BSD syntax (script -q logfile command). On Linux distros with util-linux, this requires -c flag (script -q -c "command" logfile). Without -c, the codex args were consumed by script as the logfile path. Now detects os.platform() at runtime.

Testing

• Tested on Windows 11 with Git Bash + WSL 2 (Kali Linux)
• codex-agent health, jobs, start --dry-run all verified from Git Bash
• Linux/macOS install paths unchanged (no regression)
• Install is idempotent — re-running updates cleanly

Test plan

• Fresh install from Git Bash on Windows with WSL
• codex-agent health returns "Status: Ready"
• codex-agent start "test" -d "C:\Users\..." --dry-run converts paths
• Re-run install.sh — idempotent update
• Run install.sh inside WSL directly — normal Linux flow
• Verify script command works on both macOS and Linux