fix(config_flow): no_state_source fires only when none of the three sources is present — ADB-only standalone is valid; strings/docs name all three (F2)

README.md

@@ -79,6 +79,11 @@ TiviMate (`ar.tvplayer.tv`) is the documented no-session case: it publishes
 no MediaSession on Shield Android 11 (RESEARCH_SHIELD R2), so tiers 6–7 plus
 the audio hint are what keep it visible.
 
+**Standalone setup** accepts any one of the three state sources — the Android
+TV Remote entity, the Nvidia Remote Protocol (PIN pairing), or ADB
+media-session mode (ADB enabled + host). The `no_state_source` form error
+fires only when none of the three is present; ADB-only setups are valid.
+
 ### Migration from mediasession2mqtt + universal-player glue
 
 The `mediasession2mqtt` bridge sensors and the universal media player YAML