Log window: stream the hook's logs over IPC into an in-app Log panel

Add a shared log ring (common/coop/log_ring.hpp): a lossy multi-producer /
single-consumer ring named coop_log_<pid>. The hook logs from several threads,
so producers claim a slot with fetch_add and publish each record with a
release store of its sequence; the consumer reads in order and tolerates
losing the oldest lines if it falls a whole ring behind.

The DLL's logf() now formats once and pushes every line to the ring (the file
trace stays as an opt-in mirror); the worker attaches the ring right after IPC
connect so bring-up is captured. The host (IpcServer) creates the ring at
injection time and exposes drain_logs(); a new LogPanel pulls new lines each
frame into a bounded rolling buffer and renders them with auto-scroll, a
filter, and clear. Added to the View menu (and UiState.show_log).

Verified against Phantom Brave via coop_audio_probe, which now also creates the
ring and drains it: the full hook bring-up trace streamed over IPC. All four
tests pass.

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

host/src/main.cpp

@@ -20,6 +20,7 @@
 #include "imgui_layer.hpp"
 #include "injection_panel.hpp"
 #include "input/xinput_source.hpp"
+#include "log_panel.hpp"
 #include "ui/app_chrome.hpp"
 
 namespace
@@ -68,6 +69,7 @@ int run()
 	coop::InjectionPanel injection;
 	coop::AudioPanel audio;
 	coop::CapturePanel capture;
+	coop::LogPanel log;
 	if (!capture.init(window.device()))
 	{
 		MessageBoxW(nullptr, L"Failed to initialize the video mirror.", L"CoopAllTheThings", MB_ICONERROR);
@@ -91,6 +93,7 @@ int run()
 
 		imgui.begin_frame();
 		stats.tick(ImGui::GetIO().DeltaTime * 1000.0f);
+		log.pull(injection); // drain hook log lines even while the Log window is hidden
 
 		if (ImGui::IsKeyPressed(ImGuiKey_F1, false))
 		{
@@ -120,6 +123,10 @@ int run()
 			{
 				capture.draw_ui(stats);
 			}
+			if (ui.show_log)
+			{
+				log.draw();
+			}
 		}
 		else
 		{