feat(wizard): add next-step navigation to jump back to deepest layer

Track maxReachedLayer so clicking Next from an earlier layer jumps
directly to the deepest previously visited layer, preserving state.
Reset tracking when the user changes their AI engine mode choice.

web/src/app/wizard/page.tsx

@@ -109,6 +109,16 @@ export default function WizardPage() {
   const [modelsAdded, setModelsAdded] = useState(false);
   // Sub-layer within Step 2: 0=main, 1=sub-choice, 2=provider, 3=scan, 4=config
   const [step2Layer, setStep2Layer] = useState(0);
+  const [maxReachedLayer, setMaxReachedLayer] = useState(0);
+
+  const goToStep2Layer = useCallback(
+    (layer: number) => {
+      setStep2Layer(layer);
+      setMaxReachedLayer((prev) => Math.max(prev, layer));
+    },
+    [],
+  );
+
   // Saved provider form data for back navigation
   const [savedProviderForm, setSavedProviderForm] = useState<{
     name?: string;
@@ -301,7 +311,7 @@ export default function WizardPage() {
   const handleSelectRunner = useCallback(
     (runner: string) => {
       setSelectedRunner(runner);
-      setStep2Layer(4);
+      goToStep2Layer(4);
       saveProgress({ step: 2, selected_runner: runner });
     },
     [saveProgress],
@@ -310,9 +320,17 @@ export default function WizardPage() {
   const handleAiEngineModeSelect = useCallback(
     (mode: 'orchestrated' | 'llm') => {
       setAiEngineMode(mode);
-      setStep2Layer(1);
+      setSelectedRunner(null);
+      setModelSource(null);
+      setProviderCreated(false);
+      setCreatedProviderUuid(null);
+      setModelsAdded(false);
+      setSavedProviderForm({});
+      setSavedSelectedModels(new Set());
+      setMaxReachedLayer(0);
+      goToStep2Layer(1);
     },
-    [],
+    [goToStep2Layer],
   );
 
   // ---- Navigation helpers ----
@@ -349,12 +367,16 @@ export default function WizardPage() {
   ]);
 
   const goNext = useCallback(() => {
+    if (currentStep === 2 && step2Layer < maxReachedLayer) {
+      setStep2Layer(maxReachedLayer);
+      return;
+    }
     if (currentStep < TOTAL_STEPS - 1 && canProceed()) {
       const nextStep = currentStep + 1;
       setCurrentStep(nextStep);
       saveProgress({ step: nextStep });
     }
-  }, [currentStep, canProceed, saveProgress]);
+  }, [currentStep, step2Layer, maxReachedLayer, canProceed, saveProgress]);
 
   const goPrev = useCallback(() => {
     if (currentStep === 2 && step2Layer > 0) {
@@ -568,11 +590,11 @@ export default function WizardPage() {
       if (source === 'space') {
         handleSpaceAuth();
       } else if (providerCreated && modelsAdded) {
-        setStep2Layer(4);
+        goToStep2Layer(4);
       } else if (providerCreated) {
-        setStep2Layer(3);
+        goToStep2Layer(3);
       } else {
-        setStep2Layer(2);
+        goToStep2Layer(2);
       }
     },
     [handleSpaceAuth, providerCreated, modelsAdded],
@@ -750,12 +772,12 @@ export default function WizardPage() {
             onProviderCreated={(uuid) => {
               setProviderCreated(true);
               setCreatedProviderUuid(uuid ?? null);
-              setStep2Layer(3);
+              goToStep2Layer(3);
             }}
             onModelsAdded={() => {
               setModelsAdded(true);
               setSelectedRunner('local-agent');
-              setStep2Layer(4);
+              goToStep2Layer(4);
               saveProgress({ step: 2, selected_runner: 'local-agent' });
             }}
             onResetModelSource={() => setModelSource(null)}