feat(06-04): add parameter validation and reset on model/provider change

- Add inline validation for number/integer parameters with min/max bounds
- Show red border and error text for out-of-range values
- Clear parameters when switching provider or model (schemas differ)
- Validation shows specific constraints (Min/Max values, integer requirement)

src/components/nodes/GenerateImageNode.tsx

@@ -125,7 +125,8 @@ export function GenerateImageNode({ id, data, selected }: NodeProps<NanoBananaNo
           modelId: nodeData.model || "nano-banana-pro",
           displayName: GEMINI_IMAGE_MODELS.find(m => m.value === (nodeData.model || "nano-banana-pro"))?.label || "Nano Banana Pro",
         };
-        updateNodeData(id, { selectedModel: newSelectedModel });
+        // Clear parameters when switching providers (different providers have different schemas)
+        updateNodeData(id, { selectedModel: newSelectedModel, parameters: {} });
       } else {
         // Set placeholder for external provider
         const newSelectedModel: SelectedModel = {
@@ -133,7 +134,8 @@ export function GenerateImageNode({ id, data, selected }: NodeProps<NanoBananaNo
           modelId: "",
           displayName: "Select model...",
         };
-        updateNodeData(id, { selectedModel: newSelectedModel });
+        // Clear parameters when switching providers
+        updateNodeData(id, { selectedModel: newSelectedModel, parameters: {} });
       }
     },
     [id, nodeData.model, updateNodeData]
@@ -150,7 +152,8 @@ export function GenerateImageNode({ id, data, selected }: NodeProps<NanoBananaNo
           modelId: model.id,
           displayName: model.name,
         };
-        updateNodeData(id, { selectedModel: newSelectedModel });
+        // Clear parameters when changing models (different models have different schemas)
+        updateNodeData(id, { selectedModel: newSelectedModel, parameters: {} });
       }
     },
     [id, currentProvider, externalModels, updateNodeData]

src/components/nodes/GenerateVideoNode.tsx

@@ -87,7 +87,8 @@ export function GenerateVideoNode({ id, data, selected }: NodeProps<GenerateVide
         modelId: "",
         displayName: "Select model...",
       };
-      updateNodeData(id, { selectedModel: newSelectedModel });
+      // Clear parameters when switching providers (different providers have different schemas)
+      updateNodeData(id, { selectedModel: newSelectedModel, parameters: {} });
     },
     [id, updateNodeData]
   );
@@ -103,7 +104,8 @@ export function GenerateVideoNode({ id, data, selected }: NodeProps<GenerateVide
           modelId: model.id,
           displayName: model.name,
         };
-        updateNodeData(id, { selectedModel: newSelectedModel });
+        // Clear parameters when changing models (different models have different schemas)
+        updateNodeData(id, { selectedModel: newSelectedModel, parameters: {} });
       }
     },
     [id, currentProvider, externalModels, updateNodeData]

src/components/nodes/ModelParameters.tsx

@@ -227,8 +227,24 @@ function ParameterInput({ param, value, onChange }: ParameterInputProps) {
   }
 
   if (param.type === "number" || param.type === "integer") {
-    // Number: render as number input
+    // Number: render as number input with validation
     const numValue = value !== undefined ? Number(value) : "";
+    const hasMin = param.minimum !== undefined;
+    const hasMax = param.maximum !== undefined;
+
+    // Validate current value against constraints
+    let validationError: string | null = null;
+    if (value !== undefined && value !== "" && !isNaN(Number(value))) {
+      const num = Number(value);
+      if (hasMin && num < param.minimum!) {
+        validationError = `Min: ${param.minimum}`;
+      } else if (hasMax && num > param.maximum!) {
+        validationError = `Max: ${param.maximum}`;
+      } else if (param.type === "integer" && !Number.isInteger(num)) {
+        validationError = "Must be integer";
+      }
+    }
+
     return (
       <div className="flex flex-col gap-0.5">
         <label
@@ -236,7 +252,7 @@ function ParameterInput({ param, value, onChange }: ParameterInputProps) {
           title={param.description || undefined}
         >
           {displayName}
-          {param.minimum !== undefined && param.maximum !== undefined && (
+          {hasMin && hasMax && (
             <span className="text-neutral-500">
               ({param.minimum}-{param.maximum})
             </span>
@@ -258,8 +274,15 @@ function ParameterInput({ param, value, onChange }: ParameterInputProps) {
             }
           }}
           placeholder={param.default !== undefined ? `Default: ${param.default}` : undefined}
-          className="w-full text-[9px] py-0.5 px-1 border border-neutral-700 rounded bg-neutral-900/50 focus:outline-none focus:ring-1 focus:ring-neutral-600 text-neutral-300 placeholder:text-neutral-600"
+          className={`w-full text-[9px] py-0.5 px-1 border rounded bg-neutral-900/50 focus:outline-none focus:ring-1 text-neutral-300 placeholder:text-neutral-600 ${
+            validationError
+              ? "border-red-500 focus:ring-red-500"
+              : "border-neutral-700 focus:ring-neutral-600"
+          }`}
         />
+        {validationError && (
+          <span className="text-[8px] text-red-400">{validationError}</span>
+        )}
       </div>
     );
   }