EmuThread: Run the graphics context's ThreadStart before starting the emu thread

On OpenGL the render thread's ThreadStart fills in the GL strings and
picks the buffer strategy, while the emu thread, started just before
it, could already be in NativeInitGraphics reading them. A Play report
crashed walking the strings map in BuildReportingInfo. ThreadStart also
resets the exit flags, which could undo an early exit by the emu
thread. Libretro already starts its emu thread in this order.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Core/EmuThread.cpp

@@ -79,9 +79,10 @@ static void EmuThreadFunc(GraphicsContext *graphicsContext, Application *applica
 std::thread EmuThread_Start(GraphicsContext *graphicsContext, Application *application, std::function<bool(GraphicsContext *)> frame) {
 	INFO_LOG(Log::System, "EmuTread_Start");
 	_dbg_assert_(g_emuThreadState == EmuThreadState::STOPPED);
-	std::thread emuThread = std::thread(&EmuThreadFunc, graphicsContext, application, frame);
+	// Before the emu thread exists: ThreadStart sets up state that NativeInitGraphics reads (the GL
+	// strings for reporting), and resets the exit flags the emu thread sets.
 	graphicsContext->ThreadStart();
-	return emuThread;
+	return std::thread(&EmuThreadFunc, graphicsContext, application, frame);
 }
 
 // This is useful when the render thread is in control.