fix: ESP32 Run button auto-compiles and recovers firmware after page refresh

- handleRun now auto-compiles for ESP32/QEMU boards when no firmware is
  available (same behavior as AVR/RP2040 boards)
- startBoard now reloads compiledProgram into the bridge if _pendingFirmware
  was lost (e.g. after a page refresh between compile and run)
- Adds Esp32Bridge.hasFirmware() helper used by the store check

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/editor/EditorToolbar.tsx

@@ -164,8 +164,22 @@ export const EditorToolbar = ({ consoleOpen, setConsoleOpen, compileLogs: _compi
       const board = boards.find((b) => b.id === activeBoardId);
       const isQemuBoard = board?.boardKind === 'raspberry-pi-3' || board?.boardKind === 'esp32' || board?.boardKind === 'esp32-s3';
 
-      // QEMU boards don't need compilation
+      // QEMU boards: auto-compile if no firmware available yet
       if (isQemuBoard) {
+        if (!board?.compiledProgram || codeChangedSinceLastCompile) {
+          autoRunAfterCompile.current = true;
+          await handleCompile();
+          const updatedBoard = useSimulatorStore.getState().boards.find((b) => b.id === activeBoardId);
+          if (autoRunAfterCompile.current && updatedBoard?.compiledProgram) {
+            autoRunAfterCompile.current = false;
+            trackRunSimulation(updatedBoard.boardKind);
+            startBoard(activeBoardId);
+            setMessage(null);
+          } else {
+            autoRunAfterCompile.current = false;
+          }
+          return;
+        }
         trackRunSimulation(board?.boardKind);
         startBoard(activeBoardId);
         setMessage(null);

frontend/src/simulation/Esp32Bridge.ts

@@ -240,6 +240,11 @@ export class Esp32Bridge {
     this._pendingSensors = sensors;
   }
 
+  /** Returns true if a firmware has been loaded and is ready to send. */
+  hasFirmware(): boolean {
+    return this._pendingFirmware !== null && this._pendingFirmware !== '';
+  }
+
   /**
    * Load a compiled firmware (base64-encoded .bin) into the running ESP32.
    * If not yet connected, the firmware will be sent on next connect().

frontend/src/store/useSimulatorStore.ts

@@ -669,6 +669,12 @@ export const useSimulatorStore = create<SimulatorState>((set, get) => {
           );
           esp32Bridge.wifiEnabled = hasWifi;
 
+          // Ensure firmware is loaded into the bridge (handles page-refresh case
+          // where _pendingFirmware is lost but compiledProgram is still in store).
+          if (!esp32Bridge.hasFirmware() && board.compiledProgram) {
+            esp32Bridge.loadFirmware(board.compiledProgram);
+          }
+
           esp32Bridge.connect();
         }
       } else {