Fix lint infinite loop, popover usability, debounce timing

Infinite loop (lint hammering server every 2s):
- Add applyingLints ref; set true before clearLintMarks() and
  editor.view.dispatch(tr), false after
- onUpdate returns early when applyingLints is true, so applying
  marks no longer reschedules a lint check or triggers a save

Popover disappearing before you can interact:
- Render via createPortal(…, document.body) — completely outside the
  editor DOM, no stacking context or overflow clipping can interfere
- onMouseDown={e => e.preventDefault()} on the popover prevents the
  editor from losing focus before the button click fires
- Removed setLintPopover(null) from the top of runLint — the popover
  was being force-closed on every auto-check cycle

Debounce: 1.5 s → 3 s — checks after a genuine pause, not mid-word

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

frontend/src/components/Editor.jsx

@@ -1,4 +1,5 @@
 import { forwardRef, useEffect, useRef, useImperativeHandle, useState, useCallback } from 'react'
+import { createPortal } from 'react-dom'
 import { useEditor, EditorContent, ReactNodeViewRenderer } from '@tiptap/react'
 import { Mark, mergeAttributes, getMarkRange } from '@tiptap/core'
 import StarterKit from '@tiptap/starter-kit'
@@ -113,6 +114,7 @@ const Editor = forwardRef(function Editor(
   const lintStatusRef  = useRef('idle')
   const lintDebounce   = useRef(null)
   const runLintRef     = useRef(null)   // always holds latest runLint, safe to call from onUpdate closure
+  const applyingLints  = useRef(false)  // true while we're dispatching mark transactions — skip onUpdate
 
   const editor = useEditor({
     extensions: [
@@ -127,10 +129,14 @@ const Editor = forwardRef(function Editor(
     ],
     content: '',
     onUpdate({ editor }) {
+      // Skip when the update was caused by us applying / clearing lint marks.
+      // Without this guard, dispatching mark transactions fires onUpdate which
+      // reschedules the lint check, which applies marks, which fires onUpdate… ∞
+      if (applyingLints.current) return
       onChange(stripLintMarks(editor.getJSON()))
       // Debounced auto-check: fire 1.5 s after the last keystroke
       clearTimeout(lintDebounce.current)
-      lintDebounce.current = setTimeout(() => runLintRef.current?.(), 1500)
+      lintDebounce.current = setTimeout(() => runLintRef.current?.(), 3000)
     },
   })
 
@@ -157,12 +163,15 @@ const Editor = forwardRef(function Editor(
     if (!editor || lintStatusRef.current === 'checking') return
     lintStatusRef.current = 'checking'
     setLintStatus('checking')
-    setLintPopover(null)
+    // Don't close an open popover here — it gets wiped on every auto-check
+    // and the user can't interact with it. It closes naturally on click-outside.
 
     try {
       const { text, posMap } = buildTextMap(editor.state.doc)
       if (!text.trim()) {
+        applyingLints.current = true
         clearLintMarks(editor)
+        applyingLints.current = false
         setLintCount(0)
         setLintStatus('done')
         lintStatusRef.current = 'done'
@@ -171,7 +180,9 @@ const Editor = forwardRef(function Editor(
 
       const data = await api.lintCheck(text)
 
-      // Clear old marks, then apply all new ones in one transaction
+      // Clear old marks then apply new ones — both wrapped in the flag so
+      // the resulting onUpdate calls are silently ignored.
+      applyingLints.current = true
       clearLintMarks(editor)
       const { tr, schema } = editor.state
       const lintType = schema.marks.lintError
@@ -192,11 +203,13 @@ const Editor = forwardRef(function Editor(
         }))
       }
       editor.view.dispatch(tr)
+      applyingLints.current = false
 
       setLintCount(data.matches.length)
       setLintStatus('done')
       lintStatusRef.current = 'done'
     } catch (err) {
+      applyingLints.current = false
       console.error('[lint] Check failed:', err)
       setLintStatus('idle')
       lintStatusRef.current = 'idle'
@@ -274,11 +287,13 @@ const Editor = forwardRef(function Editor(
         <div className="word-count">{wordCount.toLocaleString()} {wordCount === 1 ? 'word' : 'words'}</div>
       </div>
 
-      {lintPopover && (
+      {lintPopover && createPortal(
         <div
           className="lint-popover"
           style={{ top: lintPopover.top, left: lintPopover.left }}
-          // Stop clicks inside the popover from bubbling to the editor click handler
+          // Prevent mousedown from stealing focus away from the editor —
+          // without this the editor blurs and the popover may vanish before click fires
+          onMouseDown={e => e.preventDefault()}
           onClick={e => e.stopPropagation()}
         >
           <p className="lint-popover-msg">{lintPopover.message}</p>
@@ -293,7 +308,8 @@ const Editor = forwardRef(function Editor(
             <button className="btn btn-ghost lint-ignore" onClick={dismissLintMark}>Ignore</button>
             <button className="btn btn-ghost lint-close"  onClick={() => setLintPopover(null)}>✕</button>
           </div>
-        </div>
+        </div>,
+        document.body,
       )}
     </div>
   )