- expose AudioManager::setAudioInput() to inject custom input device

Lets a host inject e.g. NullInputDevice before start() so the default
platform microphone is not constructed, avoiding the RECORD_AUDIO
permission on Android while leaving the real speaker output in place.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/engine/agent/Agent_AudioManager.cpp

@@ -167,6 +167,12 @@ void AudioManager::stop(int usageId)
     }
 }
 
+void AudioManager::setAudioInput(Audio::PInputDevice input)
+{
+    LOCK_MANAGER;
+    mAudioInput = std::move(input);
+}
+
 void AudioManager::startPlayFile(int usageId, const std::string& path, AudioTarget target, LoopMode lm, int timelimit)
 {
     // Check if file exists

src/engine/agent/Agent_AudioManager.h

@@ -53,6 +53,11 @@ public:
     void start(int usageId);
     void stop(int usageId);
 
+    // Inject a custom input device. Must be called before start(): when set,
+    // start() skips construction of the default platform microphone. Pass an
+    // empty pointer to clear the override.
+    void setAudioInput(Audio::PInputDevice input);
+
     enum AudioTarget
     {
         atNull,