Notes: raise limits (3,000 notes, 200k chars each), reject instead of truncating oversize notes, save-error feedback, richer editor toolbar + word count, copy note; v2.42.0

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

server/routes/study-data.js

@@ -147,7 +147,11 @@ export function register(app) {
       return
     }
     const rawNote = typeof req.body?.note === 'string' ? req.body.note : ''
-    const note = rawNote.trim().slice(0, MAX_STUDY_NOTE_LENGTH)
+    const note = rawNote.trim()
+    if (note.length > MAX_STUDY_NOTE_LENGTH) {
+      res.status(413).json({ message: 'This lesson\'s notes are too long to save. Please trim some text.' })
+      return
+    }
     const notes = await loadUserNotes(user.id)
 
     if (!note) {