Audio render-hook M2: render hook + in-process self-test (concept proven)

Implements the WASAPI render-hook (hook/src/audio_hook.{hpp,cpp}) and an
in-process self-test that proves COM vtable discovery and GetBuffer/ReleaseBuffer
interception with no game and no second Steam account.

- audio_hook.cpp: anchors on IMMDevice::Activate (idx 3) off our own default
  endpoint (shared vtable), then hooks IAudioClient::Initialize (3) /
  GetService (14) and IAudioRenderClient::GetBuffer (3) / ReleaseBuffer (4) off
  live game pointers. Copies primary-stream frames into the audio ring and
  releases with AUDCLNT_BUFFERFLAGS_SILENT (+ memset belt-and-suspenders), only
  while the host-owned capture_enabled flag is set. Stream counting runs always;
  on a ring overrun it keeps playing locally rather than going silent.
- ipc_client.hpp: publish_audio_stream / note_audio_frames /
  set_audio_streams_seen write the render-stream debug fields into HookStatus.
- tests/audio_hook_test.cpp: installs the hooks, renders a tone through WASAPI
  in-process, and asserts exactly one stream, frames pushed to the ring, the
  ring carries the non-silent tone, and the primary was silenced. PASS:
  streams_seen=1, frames_captured=32640.
- plan doc: correct GetService vtable index 13 -> 14 (SetEventHandle is 13).

coop_hook DLL wiring + host consumer/fallback come next (M3).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

hook/src/ipc_client.hpp

@@ -119,6 +119,35 @@ public:
 		}
 	}
 
+	// --- Audio render-hook diagnostics -------------------------------------
+
+	// Total distinct render streams the audio hook has observed.
+	void set_audio_streams_seen(std::uint32_t count)
+	{
+		if (block_ != nullptr)
+		{
+			block_->status.audio_streams_seen = count;
+		}
+	}
+
+	// Publish a tracked stream's format/role into its debug slot.
+	void publish_audio_stream(std::uint32_t slot, const AudioStreamInfo& info)
+	{
+		if (block_ != nullptr && slot < kMaxAudioStreams)
+		{
+			block_->status.audio_streams[slot] = info;
+		}
+	}
+
+	// Update a tracked stream's cumulative frame count (host derives live/idle).
+	void note_audio_frames(std::uint32_t slot, std::uint64_t frames)
+	{
+		if (block_ != nullptr && slot < kMaxAudioStreams)
+		{
+			block_->status.audio_streams[slot].frames_rendered = frames;
+		}
+	}
+
 private:
 	SharedMemory shm_;
 	SharedBlock* block_ = nullptr;