feat(caddy): replace textarea with CodeMirror 6 editor in caddy-editor

Replaces the plain textarea on /caddy/edit with a CodeMirror 6 component
that provides live Caddyfile syntax highlighting (keywords, named matchers,
comments). The editor is dynamically imported (ssr: false) to prevent
hydration errors. The write/validate/save/reload state machine and content
flow remain unchanged.

Bundle impact: ~300 kB additional for the /caddy/edit route (CodeMirror 6
core + @uiw/react-codemirror).

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

app/caddy/_components/caddy-codemirror.tsx

@@ -0,0 +1,25 @@
+'use client'
+import CodeMirror from '@uiw/react-codemirror'
+import { caddyfileLanguage } from '@/lib/codemirror/caddyfile-mode'
+import { EditorView } from '@codemirror/view'
+
+type Props = {
+  value: string
+  onChange: (next: string) => void
+  readOnly?: boolean
+}
+
+export default function CaddyCodeMirror({ value, onChange, readOnly }: Props) {
+  return (
+    <CodeMirror
+      value={value}
+      onChange={onChange}
+      readOnly={readOnly}
+      extensions={[caddyfileLanguage, EditorView.lineWrapping]}
+      theme="dark"
+      height="480px"
+      basicSetup={{ lineNumbers: true, foldGutter: false, highlightActiveLine: !readOnly }}
+      className="rounded-lg border border-border overflow-hidden text-xs"
+    />
+  )
+}

app/caddy/_components/caddy-editor.tsx

@@ -1,11 +1,21 @@
 'use client'
 
 import { useCallback, useEffect, useState } from 'react'
+import dynamic from 'next/dynamic'
 import Link from 'next/link'
 import { useFlowRun } from '@/hooks/useFlowRun'
 import ConfirmDialog from '@/components/ConfirmDialog'
 import StreamingTerminal from '@/components/StreamingTerminal'
 
+const CaddyCodeMirror = dynamic(() => import('./caddy-codemirror'), {
+  ssr: false,
+  loading: () => (
+    <div className="h-[480px] rounded-lg border border-border bg-zinc-950 p-4 text-xs text-zinc-500">
+      Loading editor…
+    </div>
+  ),
+})
+
 type Phase = 'edit' | 'writing' | 'validating' | 'validated' | 'saving' | 'saved'
 
 type DialogPending = 'validate' | 'save' | null
@@ -106,17 +116,13 @@ export default function CaddyEditor({ initialContent, initialError }: Props) {
             </span>
           )}
         </div>
-        <textarea
+        <CaddyCodeMirror
           value={content}
-          onChange={(e) => {
-            setContent(e.target.value)
-            // Reset validated state if user edits after validation
+          onChange={(next) => {
+            setContent(next)
             if (phase === 'validated' || phase === 'saved') setPhase('edit')
           }}
           readOnly={isActive}
-          rows={24}
-          spellCheck={false}
-          className="w-full rounded-lg border border-border bg-zinc-950 p-4 font-mono text-xs text-zinc-100 focus:outline-none focus:ring-1 focus:ring-ring resize-y disabled:opacity-50"
         />
       </div>