feat(CodeEditor, MediaManager): add initial text state for editing functionality

src/app/components/CodeEditor.tsx

@@ -41,8 +41,9 @@ function prettify(text: string, mode: CodeMode): string {
 }
 
 export default function CodeEditor({ text, mode, readOnly = false, onSave }: CodeEditorProps) {
-  const [editMode, setEditMode] = useState(false);
+  const [editMode, setEditMode]       = useState(false);
-  const [saving, setSaving]     = useState(false);
+  const [editInitText, setEditInitText] = useState('');
+  const [saving, setSaving]           = useState(false);
   const editorViewRef = useRef<EditorView | null>(null);
 
   const displayText = prettify(text, mode);
@@ -61,7 +62,7 @@ export default function CodeEditor({ text, mode, readOnly = false, onSave }: Cod
         {!readOnly && (
           <div className="flex items-center gap-2 px-3 py-1.5 bg-neutral-900 border-b border-neutral-700 flex-shrink-0 text-xs">
             <button
-              onClick={() => setEditMode(true)}
+              onClick={() => { setEditInitText(displayText); setEditMode(true); }}
               className="px-2 py-1 rounded bg-neutral-700 text-neutral-300 hover:bg-neutral-600 inline-flex items-center gap-1"
             >
               <Pencil className="w-3.5 h-3.5" /> Edit
@@ -105,7 +106,7 @@ export default function CodeEditor({ text, mode, readOnly = false, onSave }: Cod
       </div>
       <div className="flex-1 overflow-hidden">
         <CodeMirror
-          defaultValue={displayText}
+          value={editInitText}
           extensions={extensions}
           theme={oneDark}
           height="100%"

src/app/components/HexEditor.tsx

@@ -297,11 +297,11 @@ export default function HexEditor({ data, readOnly = false, onSave }: HexEditorP
         {/* top spacer — 12px mimics former p-3 top padding */}
         <div style={{ height: paddingTop + 12 }} />
 
-        {cursor < 0 && firstRenderRow === 0 && (
+        {/* {cursor < 0 && firstRenderRow === 0 && (
           <div className="px-3 text-neutral-600 text-xs mb-2 font-mono">
             Click a cell to position cursor{editMode ? ' · type hex digits or ASCII to edit' : ''}
           </div>
-        )}
+        )} */}
 
         <div className="px-3 font-mono text-xs leading-5 whitespace-nowrap">
           {Array.from({ length: lastRenderRow - firstRenderRow }, (_, i) => {

src/app/components/MediaManager.tsx

@@ -187,8 +187,9 @@ const CM_THEME = EditorView.theme({
 });
 
 function MarkdownEditor({ text, onSave }: { text: string; onSave?: (s: string) => Promise<void> }) {
-  const [editMode, setEditMode] = useState(false);
+  const [editMode, setEditMode]       = useState(false);
-  const [saving, setSaving]     = useState(false);
+  const [editInitText, setEditInitText] = useState('');
+  const [saving, setSaving]           = useState(false);
   const editorViewRef = useRef<EditorView | null>(null);
 
   const save = async () => {
@@ -203,7 +204,7 @@ function MarkdownEditor({ text, onSave }: { text: string; onSave?: (s: string) =
       <div className="flex items-center gap-2 px-3 py-1.5 bg-neutral-900 border-b border-neutral-700 flex-shrink-0 text-xs">
         {onSave && (
           <button
-            onClick={() => setEditMode(v => !v)}
+            onClick={() => { if (!editMode) setEditInitText(text); setEditMode(v => !v); }}
             className={editMode
               ? 'px-2 py-1 rounded bg-amber-600 text-white inline-flex items-center gap-1'
               : 'px-2 py-1 rounded bg-neutral-700 text-neutral-300 hover:bg-neutral-600 inline-flex items-center gap-1'}
@@ -222,7 +223,7 @@ function MarkdownEditor({ text, onSave }: { text: string; onSave?: (s: string) =
       {editMode ? (
         <div className="flex-1 overflow-hidden">
           <CodeMirror
-            defaultValue={text}
+            value={editInitText}
             extensions={[CM_THEME]}
             theme={oneDark}
             height="100%"