fix: show helpful message when template has no parameters

Instead of an empty gap between header and Generate button, display
a small info box explaining no parameters are needed.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/scripts/ScriptParameterForm.tsx

@@ -1,3 +1,4 @@
+import { Terminal } from 'lucide-react'
 import { useScriptGeneratorStore } from '@/store/scriptGeneratorStore'
 import { ScriptParameterField } from './ScriptParameterField'
 import type { ScriptParametersSchema, ScriptParameter } from '@/types'
@@ -40,6 +41,17 @@ export function ScriptParameterForm({ canGenerate }: Props) {
     />
   )
 
+  if (parameters.length === 0) {
+    return (
+      <div className="flex items-center gap-2 rounded-lg border border-border bg-white/[0.02] px-3 py-3">
+        <Terminal size={14} className="text-muted-foreground shrink-0" />
+        <p className="text-xs text-muted-foreground">
+          This template has no parameters — click <span className="text-foreground font-medium">Generate</span> to produce the script.
+        </p>
+      </div>
+    )
+  }
+
   return (
     <div className="flex flex-col gap-4">
       {ungrouped.map(renderParam)}