Audio render-hook M4: audio panel source indicator + stream-count debug view

Surfaces the render-hook diagnostics in the Audio panel.

- HookStatusView / IpcServer::hook_status(): carry audio_streams_seen +
  audio_streams[] from the hook's back-channel.
- InjectionPanel: expose hook_status() so the audio panel can read the counts.
- AudioPanel::draw_ui(HookStatusView): show the active Source (green Hooked
  vs amber Loopback); only warn about the local echo on the loopback path. Add
  the required render-stream table: one row per stream with format, cumulative
  frames, the primary tagged, and a live/idle dot derived from frame-count
  deltas. Notes overflow when the game exceeds kMaxAudioStreams slots.

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

host/src/audio_panel.hpp

@@ -1,10 +1,14 @@
-// Owns the audio-mirror pipeline (WASAPI process loopback + re-render) and its
-// UI. The target process is derived from the injected game's window.
+// Owns the audio-mirror pipeline (render-hook ring or WASAPI process loopback +
+// re-render) and its UI. The target process is derived from the injected game's
+// window; the render-stream debug view reads the hook's diagnostics back-channel.
 #pragma once
 
+#include <cstdint>
+
 #include <windows.h>
 
 #include "audio/audio_loopback.hpp"
+#include "ipc/ipc_server.hpp"
 
 namespace coop
 {
@@ -19,12 +23,16 @@ public:
 		target_ = target;
 	}
 
-	void draw_ui();
+	// `status` is the hook's back-channel, for the render-stream debug view.
+	void draw_ui(const HookStatusView& status);
 
 private:
 	HWND target_ = nullptr;
 	bool enabled_ = false;
 	AudioMirror mirror_;
+
+	// Previous per-stream frame counts, to flag streams as live (advancing).
+	std::uint64_t prev_frames_[kMaxAudioStreams] = {};
 };
 
 } // namespace coop