Make "Start without state" always enabled (#360)

The menu item now works whether the machine is running or not. bootFromScratch() awaits stopEmulator() first (a no-op when already stopped), so invoking it mid-session saves the current state, tears down the running VM, and boots a fresh one.

src/main/menu.ts

@@ -137,7 +137,6 @@ async function createMenu({ isRunning } = { isRunning: false }) {
         {
           label: "Start without state",
           click: () => send(IPC_COMMANDS.MACHINE_BOOT_FROM_SCRATCH),
-          enabled: !isRunning,
         },
         {
           label: "Restart",

src/renderer/emulator.tsx

@@ -314,7 +314,8 @@ export class Emulator extends React.Component<{}, EmulatorState> {
   /**
    * Boot the emulator without restoring state
    */
-  public bootFromScratch() {
+  public async bootFromScratch() {
+    await this.stopEmulator();
     this.setState({ isBootingFresh: true });
     this.startEmulator();
   }