Add build tags to separate Unix and Windows process handling in pkg/php:
- services_unix.go: Unix-specific process group handling (Setpgid, Getpgid, Kill)
- services_windows.go: Windows-compatible alternatives using os.Signal
- services.go: Use platform-agnostic helper functions
The pkg/php package now compiles on Windows. Process termination works
via os.Interrupt/os.Kill instead of Unix signals.
Fixes#56
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
