fix: add Windows compatibility to hook scripts

[DIV7NE]

Fixes #109

The hook scripts fail on Windows due to Unix-specific APIs:

• os.setsid doesn't exist on Windows
• signal.SIGKILL doesn't exist on Windows
• Hardcoded /tmp/ paths don't exist on Windows
• subprocess.Popen can't find .cmd files without shell=True

Changes:

• Use tempfile.gettempdir() for cross-platform temp paths
• Add find_mgrep_executable() to locate mgrep.cmd on Windows
• Use shell=True + CREATE_NEW_PROCESS_GROUP on Windows
• Use taskkill instead of SIGKILL on Windows
• Add graceful error handling

Tested on Windows 11 with Python 3.14 and mgrep 0.1.6.

---

Note

Adds Windows support and hardens the mgrep hook flow.

• Use tempfile.gettempdir() for PID/log files; replace hardcoded /tmp/*
• New find_mgrep_executable() resolves mgrep/mgrep.cmd (including %APPDATA%\npm)
• Windows-specific spawn: shell=True with CREATE_NEW_PROCESS_GROUP | DETACHED_PROCESS; Unix uses preexec_fn=os.setsid
• Cross-platform termination: taskkill /F /PID on Windows; SIGKILL on Unix
• Better resilience: handle missing payloads, skip when mgrep not found, avoid duplicate sessions via PID file, structured hook response always printed, expanded debug logging

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[cursor]

Windows taskkill result ignored causing false success reporting

The kill_process function has inconsistent behavior between platforms. On Windows, subprocess.run with check=False ignores taskkill's exit code, so the function always returns True even when the kill fails (e.g., process not found or access denied). On Unix, os.kill properly raises ProcessLookupError when the process doesn't exist, returning False. This causes incorrect "Killed mgrep watch process" logging on Windows and could lead to orphaned processes if taskkill fails but the PID file is still deleted.