Studio: auto-switch Easy mode to Runs pane on run start

Easy mode had no progress island or canvas overlay, so after clicking Run
the only visible state was the button label flipping to "Running..." while
the screen otherwise stayed identical. This reads as stuck even though the
job is progressing.

Wire an onExecutionStart callback from recipe-studio-page.tsx through to
useRecipeExecutions so that when a run is kicked off from easy mode, the
page flips to the executions view where the Runs sidebar, progress bar,
rate/ETA panel, and live log are rendered. Advanced/editor mode keeps its
existing behavior and stays on the canvas (it already has the floating
ExecutionProgressIsland).

studio/frontend/src/features/recipe-studio/recipe-studio-page.tsx

@@ -227,6 +227,15 @@ export function RecipeStudioPage({
     },
     [viewModeStorageKey],
   );
+  // Easy mode has no canvas overlay/progress island, so once a run starts the
+  // user sees the Run button stuck on "Running..." with nothing else changing.
+  // Flip to the Runs pane so they land where progress is actually rendered.
+  // Advanced (editor) keeps its island and stays put.
+  const handleExecutionStart = useCallback(() => {
+    setActiveView((currentView) =>
+      currentView === "easy" ? "executions" : currentView,
+    );
+  }, [setActiveView]);
   const [processorsOpen, setProcessorsOpen] = useState(false);
   const [interactive, setInteractive] = useState(true);
   const [runtimeIslandMinimized, setRuntimeIslandMinimized] = useState(false);
@@ -364,6 +373,7 @@ export function RecipeStudioPage({
     resetRecipe,
     loadRecipe,
     getCurrentPayloadFromStore,
+    onExecutionStart: handleExecutionStart,
   });
   const {
     activeExecution,