Address review: per-variant wifi src, real SSID reply, rename PicoW env

variants/thinknode_m2/platformio.ini

@@ -184,6 +184,7 @@ build_flags =
   -D WIFI_PWD='"mypwd"'
 build_src_filter = ${ThinkNode_M2.build_src_filter}
   +<helpers/esp32/*.cpp>
+  +<helpers/wifi/*.cpp>
   +<helpers/ui/MomentaryButton.cpp>
   +<helpers/ui/buzzer.cpp>
   +<../examples/companion_radio/*.cpp>