docs: state the default-device audio assumption (no device probing, no OS-level audio debugging)

README.md

@@ -28,6 +28,14 @@ ytLlive assumes you already have a YouTube creator account — connecting uses "
 to link that existing account. **ytLlive does not create accounts.** If you don't have a YouTube
 channel yet, set one up on YouTube first, then connect it here.
 
+## Audio Assumption
+
+ytLlive uses your **default** microphone and desktop/game output — it never hunts for a device or
+contends for one. **It assumes your audio is already configured and working** (default input and
+output set, not hijacked by another app). Audio issues are a Windows/device matter outside ytLlive's
+scope: we don't debug, detect, or try to fix them. If it doesn't sound right, fix the system's audio
+settings first — it's on the OS, not on us.
+
 ## Run
 
 ```bash

ViewModels/MainViewModel.Audio.cs

@@ -415,6 +415,7 @@ public partial class MainViewModel
                 return;
             }
             _audioMixer.Start();
+            AppLog.Write("Audio: using system default mic + default output — assuming they are configured and available (device issues are out of scope).");
         }
         catch (Exception ex)
         {