docs: explain fallback limits for registered tuner inputs

docs/devices/haam-r4.md

@@ -43,6 +43,15 @@ channel collection, the row opens the normal Live TV app. It does not silently
 choose another tuner. Leave `live_tv_input_id` empty to retain existing automatic
 selection and OEM routing.
 
+An input being registered does not mean it is configured or usable. A wrong but
+existing ID can be accepted by the Live TV app and open an empty tuner setup
+screen, so the fallback above does not run. Use a tuner verified on your own TV,
+or clear `live_tv_input_id` to restore automatic selection. In a
+[community check on a Philips 65PUS8102/12](https://github.com/Gathin23/cleanyourtv/pull/534#issuecomment-6315693748)
+(Android TV 8.0, TPM171E / MediaTek), HW0 opened the player while the registered
+HW9 opened an empty setup screen. This was an intent and focused-activity check,
+not a picture check, and those IDs must not be copied to other TVs.
+
 This selects an input, not a particular programme, satellite orbital position or
 frequency. The TV's own channel database and player still control tuning. It does
 not scan, renumber channels, replace a tuner driver or change dish settings.

launcher/app/src/main/res/values/config.xml

@@ -50,7 +50,9 @@
          a TV with separate antenna, cable and satellite tuners. It opens that input's channel
          collection, restricted to live_tv_package. Empty keeps automatic selection and its existing
          OEM passthrough route. If the ID is absent or the app cannot handle the collection, open
-         the Live TV app normally instead of selecting a different input. See docs/devices/haam-r4.md. -->
+         the Live TV app normally instead of selecting a different input. A wrong but registered ID
+         can open the app's tuner setup screen instead; that is not detected as a fallback condition.
+         Use a verified input ID, or leave this empty. See docs/devices/haam-r4.md. -->
     <string name="live_tv_input_id" translatable="false"></string>
 
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