Run Mastercam 2020 headless: NET-Hook add-in + hidden Windows desktop, job passed via environment variable

1. Write a NET-Hook add-in (class MyHook : NetHook3App, Run(int param)) that reads a JSON job path from an environment variable (e.g. MCJOB), executes steps (open STEP/.mcam, machine group, stock, geometry, tools, operations, regen, post, saveas, screenshot), writes <job>.log, and writes <job>.done with a status at the end, then quits.
2. Launch Mastercam on a private desktop with the config and the hook DLL on the command line:

hdesk = u32.CreateDesktopW("MCHIDDEN", None, None, 0, 0x10000000, None)   # GENERIC_ALL
si = STARTUPINFO(); si.cb = ctypes.sizeof(si); si.lpDesktop = "WinSta0\\MCHIDDEN"
env = dict(os.environ, MCJOB=job)
blk = ctypes.create_unicode_buffer("".join(f"{k}={v}\0" for k, v in env.items()) + "\0")
cmd = f'"{MC_EXE}" "{CONFIG}" "{HOOK_DLL}"'
k32.CreateProcessW(None, ctypes.c_wchar_p(cmd), None, None, False,
                   0x00000400 | 0x00004000,   # CREATE_UNICODE_ENVIRONMENT | BELOW_NORMAL_PRIORITY_CLASS
                   blk, os.path.dirname(MC_EXE), ctypes.byref(si), ctypes.byref(pi))

3. Poll for <job>.done or process exit with a timeout; enumerate the hidden desktop's windows each loop and log/auto-confirm only your own dialogs; on timeout kill only the process tree you started.
4. Use a copy of the user's .config with first-run/startup prompts disabled so nothing modal appears.
5. For many small jobs, use a "serve" mode: Run() installs a WinForms Timer that polls a queue folder and returns immediately, so Mastercam's message loop stays responsive instead of blocking inside Run().