Fix cursor position reset in editor after typing

The parsedContent watcher was calling highlight() which replaces innerHTML,
resetting cursor position. Changed to only call markErrors() directly since
we only need to update error markings when content changes.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: stared

src/components/MarkdownEditor.vue

@@ -283,10 +283,11 @@ watch(colorArray, () => {
   }
 }, { deep: true })
 
-// Re-highlight when parsed content changes (for error marking)
+// Update error markings when parsed content changes (without re-highlighting to preserve cursor)
 watch(parsedContent, () => {
-  if (codeRef.value) {
-    highlight(codeRef.value)
+  if (codeRef.value && parsedContent.value) {
+    const code = codeRef.value.textContent || ''
+    markErrors(codeRef.value, code, parsedContent.value.errors)
   }
 })