Windows: stop/status/restart commands broken due to Unix-only process management

[Alexander-He]

Description

On Windows, the weclaw stop, weclaw status, and weclaw restart commands do not work correctly. The process management code in cmd/start.go uses Unix-only APIs (syscall.SIGTERM, p.Signal(0), pkill) that are either unavailable or behave differently on Windows.

Affected Commands

1. weclaw stop

• Prints "weclaw stopped" but does not actually kill the process
• stopAllWeclaw() uses p.Signal(syscall.SIGTERM) which does not terminate processes on Windows
• Falls back to exec.Command("pkill", ...) which is a Unix-only command — will fail silently on Windows
• Verified: after running weclaw stop, Get-Process -Name weclaw still shows the process running

2. weclaw status

• Prints "weclaw is not running" even when the process is actively running
• processExists() uses os.FindProcess(pid) + p.Signal(syscall.Signal(0))
• On Windows, os.FindProcess always succeeds regardless of whether the process exists, and Signal(0) is not a valid operation
• Verified: weclaw status reports "not running" while the process is actually processing WeChat messages

3. weclaw restart

• Inherits both broken behaviors from stopAllWeclaw() and processExists()
• The 10-second wait loop (20 x 500ms) will always time out because processExists() never returns false

Root Cause

All affected functions are in cmd/start.go:

• processExists(pid int) bool (line 426-433) — uses Unix signal 0 probe
• stopAllWeclaw() (line 436-452) — uses SIGTERM + pkill

Suggested Fix

1. processExists() on Windows: Use OpenProcess API via syscall, or fall back to tasklist /FI "PID eq %d"
2. stopAllWeclaw() on Windows: Use taskkill /F /PID %d or TerminateProcess instead of SIGTERM + pkill
3. Use build tags (//go:build windows) for platform-specific implementations, similar to the existing proc_windows.go

Environment

• OS: Windows 11 (amd64)
• WeClaw version: v0.7.1 (pre-built Windows binary)
• Reproduce: run weclaw start, then weclaw status or weclaw stop

Workaround

Stop-Process -Name weclaw   # instead of weclaw stop
Get-Process -Name weclaw     # instead of weclaw status

[Alexander-He]

Fixed in PR #75 — moved processExists() and stopAllWeclaw() to platform-specific files with build tags. Windows now uses tasklist/taskkill instead of Unix signals and pkill.