fix(overlay): send session help commands before closing the modal

- Closing help first could destroy the dedicated modal window on Linux/Windows, dropping the IPC for the selected command
- dispatchConfiguredMpvCommand now returns a promise so help closes only after subtitle seek + re-pause are sent
- Add test asserting IPC order for a paused subtitle seek

src/renderer/handlers/keyboard.ts

@@ -258,7 +258,7 @@ export function createKeyboardHandlers(
     }
 
     if (binding.actionType === 'mpv-command') {
-      dispatchConfiguredMpvCommand(binding.command, {
+      void dispatchConfiguredMpvCommand(binding.command, {
         getPlaybackPaused: options.getPlaybackPaused,
         sendMpvCommand: (command) => window.electronAPI.sendMpvCommand(command),
       });