Auto-check after every word; disable browser spellcheck

- spellCheck={false} on EditorContent — LanguageTool's wavy marks
  take over entirely, no double-squiggle confusion
- onUpdate schedules runLint() 1.5 s after the last keystroke via
  lintDebounce ref; typing resets the timer so it only fires when
  the writer pauses (naturally after finishing a word or sentence)
- runLintRef kept in sync with useEffect so the stale onUpdate
  closure always calls the latest runLint
- Timer cleaned up on unmount

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

frontend/src/components/Editor.jsx

@@ -111,6 +111,8 @@ const Editor = forwardRef(function Editor(
   const [lintCount,  setLintCount]      = useState(0)
   const [lintPopover, setLintPopover]   = useState(null)     // { top, left, message, replacements, from, to }
   const lintStatusRef  = useRef('idle')
+  const lintDebounce   = useRef(null)
+  const runLintRef     = useRef(null)   // always holds latest runLint, safe to call from onUpdate closure
 
   const editor = useEditor({
     extensions: [
@@ -126,11 +128,9 @@ const Editor = forwardRef(function Editor(
     content: '',
     onUpdate({ editor }) {
       onChange(stripLintMarks(editor.getJSON()))
-      // Mark results as stale when the user edits so they know to re-check
-      if (lintStatusRef.current === 'done') {
-        lintStatusRef.current = 'stale'
-        setLintStatus('stale')
-      }
+      // Debounced auto-check: fire 1.5 s after the last keystroke
+      clearTimeout(lintDebounce.current)
+      lintDebounce.current = setTimeout(() => runLintRef.current?.(), 1500)
     },
   })
 
@@ -153,6 +153,11 @@ const Editor = forwardRef(function Editor(
   }, [editor, content])
 
   // ── Lint check ───────────────────────────────────────────────────────────
+  // Keep ref in sync so the onUpdate closure (which never re-captures) always
+  // calls the latest version of runLint.
+  useEffect(() => { runLintRef.current = runLint }, [runLint])
+  useEffect(() => () => clearTimeout(lintDebounce.current), [])
+
   const runLint = useCallback(async () => {
     if (!editor || lintStatusRef.current === 'checking') return
     lintStatusRef.current = 'checking'
@@ -265,7 +270,7 @@ const Editor = forwardRef(function Editor(
         lintCount={lintCount}
       />
       <div className="editor-wrap" onClick={handleEditorClick}>
-        <EditorContent editor={editor} className="editor-body" />
+        <EditorContent editor={editor} className="editor-body" spellCheck={false} />
         <div className="word-count">{wordCount.toLocaleString()} {wordCount === 1 ? 'word' : 'words'}</div>
       </div>