feat: add ScriptPreview with live substitution and copy

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/scripts/ScriptPreview.tsx

@@ -0,0 +1,56 @@
+import { useState } from 'react'
+import { Copy, Check } from 'lucide-react'
+import { useScriptGeneratorStore } from '@/store/scriptGeneratorStore'
+import { PowerShellHighlighter } from './PowerShellHighlighter'
+import type { ScriptParametersSchema } from '@/types'
+
+export function ScriptPreview() {
+  const selectedTemplate = useScriptGeneratorStore(s => s.selectedTemplate)
+  const paramValues = useScriptGeneratorStore(s => s.paramValues)
+  const generatedScript = useScriptGeneratorStore(s => s.generatedScript)
+  const [copied, setCopied] = useState(false)
+
+  if (!selectedTemplate) return null
+
+  // Compute the displayed script
+  let displayScript: string
+  if (generatedScript !== null) {
+    displayScript = generatedScript
+  } else {
+    // Draft mode: client-side {{key}} substitution
+    const schema = selectedTemplate.parameters_schema as ScriptParametersSchema
+    const parameters = schema?.parameters ?? []
+    displayScript = selectedTemplate.script_body
+    for (const param of parameters) {
+      const placeholder = `{{${param.key}}}`
+      const replacement = param.sensitive
+        ? '****'
+        : (paramValues[param.key] ?? '')
+      displayScript = displayScript.replaceAll(placeholder, replacement || placeholder)
+    }
+  }
+
+  const handleCopy = async () => {
+    try {
+      await navigator.clipboard.writeText(displayScript)
+      setCopied(true)
+      setTimeout(() => setCopied(false), 2000)
+    } catch {
+      // silently fail — no error displayed
+    }
+  }
+
+  return (
+    <div className="relative">
+      <button
+        onClick={handleCopy}
+        className="absolute top-3 right-3 z-10 p-1.5 rounded-md text-muted-foreground hover:text-foreground hover:bg-white/5 transition-colors"
+        title={copied ? 'Copied!' : 'Copy to clipboard'}
+        aria-label={copied ? 'Copied!' : 'Copy to clipboard'}
+      >
+        {copied ? <Check size={14} className="text-emerald-400" /> : <Copy size={14} />}
+      </button>
+      <PowerShellHighlighter script={displayScript} />
+    </div>
+  )
+}