isProcessRunning() previously only checked whether a PID existed via signal(0)/OpenProcess, without confirming the process was actually picoclaw. When the PID was reused by an unrelated process (e.g., systemd-resolved after a kill -9), the gateway would refuse to start with 'already running'.
Add isPicoclawProcess() that verifies the process name matches picoclaw:
- Unix: reads /proc/<pid>/comm
- Windows: calls QueryFullProcessImageNameW
If the running process is not picoclaw, treat the PID file as stale and proceed with normal startup. Falls back to trusting the liveness check when identity verification is unavailable (e.g., /proc unreadable, API call fails).
Fixes#2720.