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.
- treat `EPERM` from `signal(0)` as “process exists” on Unix
- classify malformed PID files as invalid and auto-remove them during read
- keep cached `pidData` only for transient races and downgrade `running` to `stopped` when the tracked process is gone
- refresh PID data on WebSocket proxy requests and reject stale cached gateway state
- add regression tests for invalid PID files, status downgrade, on-demand PID loading, and stale proxy rejection