On a freshly-flashed OpenWrt router, radio0 is disabled by default so
iw dev returns empty. Detect the PHY via /sys/class/ieee80211/, enable
radio0, run `wifi up`, then poll up to 8s for netifd to create the
virtual interface before handing it to iwinfo scan.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>