Address review feedback on rumble forwarding PR

- Drop Tick()/m_wantsGameMode auto-enable machinery (out of scope for
  this PR — belongs in a separate submission)
- Remove unused CMD_TRIGGER_RUMBLE constant
- Fix WriteOutputReport comment to accurately describe padding behaviour
- Fix CancelIo OVERLAPPED use-after-free: drain with GetOverlappedResult
  before the stack OVERLAPPED goes out of scope
- Strip redundant /wd4819 /wd4828 MSVC flags; /utf-8 already covers them
- Add comment to HeartbeatLoop explaining the 40 ms tick rationale

Co-Authored-By: Dylan Deverill <ddeverill@gmail.com>

src/app/ControllerManager.cpp

@@ -20,24 +20,9 @@ void ControllerManager::OnDeviceChange() {
         TryOpen();
     else if (g_ctrl && !g_ctrl->IsOpen())
         Close(/*restoreLizard=*/false);
-
-    if (m_connected && m_wantsGameMode && !m_gameModeActive)
-        EnableGameMode();
-}
-
-void ControllerManager::Tick() {
-    if (!m_connected) {
-        TryOpen();
-    } else if (g_ctrl && !g_ctrl->IsOpen()) {
-        Close(/*restoreLizard=*/false);
-    }
-
-    if (m_connected && m_wantsGameMode && !m_gameModeActive)
-        EnableGameMode();
 }
 
 void ControllerManager::EnableGameMode() {
-    m_wantsGameMode = true;
     if (!m_connected || m_gameModeActive) return;
     if (!g_ctrl->DisableLizardMode()) return;
 
@@ -67,7 +52,6 @@ void ControllerManager::EnableGameMode() {
 }
 
 void ControllerManager::DisableGameMode() {
-    m_wantsGameMode = false;
     if (!m_gameModeActive) return;
     StopReadLoop();
     if (g_ctrl && g_ctrl->IsOpen())
@@ -99,8 +83,6 @@ void ControllerManager::TryOpen() {
     if (g_ctrl->Open()) {
         m_connected = true;
         m_onStateChanged(m_connected, m_gameModeActive, false);
-        if (m_wantsGameMode && !m_gameModeActive)
-            EnableGameMode();
     }
 }