fix: handle root edits when markdown has no H1 line

trySurgicalEdit detects root via mind.nodeData reference (more reliable
than meta.kind which can fall through to 'block' after refreshMetadata).
editNodeText falls back to inserting `# topic` at the document start
when root.startLine is missing, so renaming root in an empty document
produces a real heading instead of leaving the change unsaved.

Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: Andrei Kvapil <kvapss@gmail.com>

Author: kvaps

src/components/MindMap.vue

@@ -166,7 +166,14 @@ function trySurgicalEdit(op: unknown): boolean {
 
   if (o.name === 'finishEdit') {
     const meta = o.obj?.metadata as NodeMeta | undefined
-    if (!meta || meta.startLine < 0) return false
+    if (!meta) return false
+    const isRoot = !!mind && o.obj === mind.nodeData
+    if (isRoot && meta.startLine < 0) {
+      const forced: NodeMeta = { ...meta, kind: 'root' }
+      if (typeof o.obj?.topic !== 'string') return false
+      return commitMarkdown(editNodeText(store.markdown, forced, o.obj.topic))
+    }
+    if (meta.startLine < 0) return false
     if (typeof o.obj?.topic !== 'string') return false
     return commitMarkdown(editNodeText(store.markdown, meta, o.obj.topic))
   }

src/utils/surgical.ts

@@ -18,7 +18,13 @@ function escapeNewlinesForListItem(text: string, indent: number): string {
 }
 
 export function editNodeText(markdown: string, meta: NodeMeta, newText: string): string {
-  if (meta.startLine < 0) return markdown
+  if (meta.startLine < 0) {
+    if (meta.kind !== 'root') return markdown
+    const head = `# ${newText.split('\n')[0]}`
+    const rest = markdown.trim()
+    if (!rest) return head + '\n'
+    return head + '\n\n' + rest + (rest.endsWith('\n') ? '' : '\n')
+  }
   const lines = markdown.split('\n')
   const firstLine = lines[meta.startLine]
   if (firstLine === undefined) return markdown