In containers, PIDs can be recycled quickly after restarts. When a container
restarts, a different process might get the same PID as the previous gateway,
causing the lock check to incorrectly think the old gateway is still running.
This fix adds isGatewayProcess() which verifies on Linux that the PID actually
belongs to a clawdbot gateway by checking /proc/PID/cmdline. If the cmdline
doesn't contain 'clawdbot' or 'gateway', we assume the lock is stale.
Fixes gateway boot-loop in Docker/Fly.io deployments.
