fix: wifi scan no longer interrupts connecting/DHCP/connected state
The JS pieces call wifi.scan() every ~2s which was sending WIFI_CMD_SCAN
to the worker thread, interrupting in-progress WPA handshake and DHCP.
Now wifi_scan() is a no-op while connecting or already connected.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>