fix(wizard): off-by-one causing step 7/6 display and broken completion

- nextStep() was allowing currentStep to reach steps.length (6), past
  the last step index (5), showing "步骤 7/6:" with empty content area
- On the last step, nextStep now triggers handleSubmit() directly
  instead of navigating to a phantom step 6
- Footer button condition changed: "完成" shows on last step instead
  of after it, keeping error/success messages visible
- Added error logging in catch block (was silently swallowing errors)

desktop/src/components/AgentOnboardingWizard.tsx

@@ -192,7 +192,12 @@ export function AgentOnboardingWizard({ isOpen, onClose, onSuccess }: AgentOnboa
   // Navigate to next step
   const nextStep = () => {
     if (validateStep(currentStep)) {
-      setCurrentStep((prev) => Math.min(prev + 1, steps.length));
+      // On the last step, trigger submit instead of navigating past it
+      if (currentStep === steps.length - 1) {
+        handleSubmit();
+      } else {
+        setCurrentStep((prev) => prev + 1);
+      }
     }
   };
 
@@ -290,7 +295,8 @@ export function AgentOnboardingWizard({ isOpen, onClose, onSuccess }: AgentOnboa
       } else {
         setSubmitStatus('error');
       }
-    } catch {
+    } catch (err) {
+      log.error('Agent creation failed:', err);
       setSubmitStatus('error');
     }
   };
@@ -723,7 +729,7 @@ export function AgentOnboardingWizard({ isOpen, onClose, onSuccess }: AgentOnboa
           </button>
 
           <div className="flex items-center gap-2">
-            {currentStep < steps.length ? (
+            {currentStep < steps.length - 1 ? (
               <button
                 type="button"
                 onClick={nextStep}