audio: retain WASAPI clients only after initialization (#807)

## Link to GitHub Issue or related Pull Request, if one exists
Fixes #782 

## Description of change

This addresses an issue only seen on Linux + WINE.

Defer retaining WASAPI clients until `Initialize` succeeds.

Before this PR, temporary clients created during DirectShow device
capability probing were retained as active audio clients, causing
Wine/Linux crashes in DDR and popn.

Also covers IAudioClient3, dummy, ASIO, WaveOut, and null-device
initialization paths, for consistency.

## Testing
WIP

src/spice2x/hooks/audio/backends/wasapi/dummy_audio_client.cpp

@@ -75,13 +75,17 @@ HRESULT STDMETHODCALLTYPE DummyIAudioClient::Initialize(
     log_info("audio::wasapi", "IAudioClient::Initialize hook hit");
     print_format(ShareMode, StreamFlags, hnsBufferDuration, hnsPeriodicity, pFormat);
 
-    CHECK_RESULT(this->backend->on_initialize(
+    HRESULT ret = this->backend->on_initialize(
         &ShareMode,
         &StreamFlags,
         &hnsBufferDuration,
         &hnsPeriodicity,
         pFormat,
-        AudioSessionGuid));
+        AudioSessionGuid);
+    if (SUCCEEDED(ret)) {
+        hooks::audio::set_active_client(this, "DummyIAudioClient::Initialize");
+    }
+    CHECK_RESULT(ret);
 }
 HRESULT STDMETHODCALLTYPE DummyIAudioClient::GetBufferSize(UINT32 *pNumBufferFrames) {
     static std::once_flag printed;