Code-review fixes for collocation coach + vocab garden

Correctness:
- useCheckpoint: clear the busy flag unconditionally so overlapping
  explicit passes don't strand each other's spinner; explicit actions
  now also supersede a queued auto-check and clear the stranded
  "checking" dot. Deduped runVoice/runCollocation into runExplicitPass.
- EditorCore: token-guard the auto-capture so a late capture can't
  resurrect a removed word; move toggleSaveWord side effects out of the
  setWordInfo updater (StrictMode double-fire); fix sentenceAround offset
  desync via shared exampleAt (textBetween + parentOffset, single resolve);
  optimistic saved state so the heart doesn't flash unsaved.
- vocab capture: normalize word to lower+trim (matches lexicon) so
  "Apple"/"apple" don't make duplicate cards; check rows.Err() in queryList.
- GardenPanel: Promise.allSettled so a /due failure doesn't blank the
  whole garden; scrim click during review ends the review (mirrors Esc);
  gate footer on !error; O(1) due lookup via a Set.

Features requested in review:
- Definition-only review card: add vocab_words.definition (migration
  0007) as an English fallback meaning, threaded through capture and used
  by review/garden when there's no Chinese gloss.
- Scheduler caps: maxEase 3.0 + maxInterval 365d so "easy" growth can't
  push a word out of rotation for years.

Tests: TestCaptureCaseInsensitive, TestCaptureStoresDefinitionFallback,
TestCapsBoundGrowth. go build/vet/test, tsc, vitest 51/51, vite build clean.

Claude-Session: https://claude.ai/code/session_016Yr6jELuRc7hyzYLccQKZd

internal/vocab/handlers.go

@@ -20,6 +20,7 @@ type Word struct {
 	ID           string     `json:"id"`
 	Word         string     `json:"word"`
 	Gloss        string     `json:"gloss"`
+	Definition   string     `json:"definition"` // English fallback meaning when there's no Chinese gloss
 	Phonetic     string     `json:"phonetic"`
 	Example      string     `json:"example"`
 	DocID        *string    `json:"doc_id"`
@@ -51,7 +52,7 @@ func (h *Handler) Routes() chi.Router {
 	return r
 }
 
-const vocabColumns = `id, word, gloss, phonetic, example, doc_id,
+const vocabColumns = `id, word, gloss, definition, phonetic, example, doc_id,
 	due_at, interval_days, ease, reps, lapses, last_reviewed, created_at`
 
 func scanWord(s interface {
@@ -59,7 +60,7 @@ func scanWord(s interface {
 }) (Word, error) {
 	var w Word
 	err := s.Scan(
-		&w.ID, &w.Word, &w.Gloss, &w.Phonetic, &w.Example, &w.DocID,
+		&w.ID, &w.Word, &w.Gloss, &w.Definition, &w.Phonetic, &w.Example, &w.DocID,
 		&w.DueAt, &w.IntervalDays, &w.Ease, &w.Reps, &w.Lapses, &w.LastReviewed, &w.CreatedAt,
 	)
 	return w, err
@@ -93,15 +94,20 @@ func (h *Handler) queryList(w http.ResponseWriter, query string, args ...any) {
 		}
 		out = append(out, word)
 	}
+	if err := rows.Err(); err != nil {
+		serverError(w, err)
+		return
+	}
 	writeJSON(w, http.StatusOK, out)
 }
 
 type captureRequest struct {
-	Word     string  `json:"word"`
-	Gloss    string  `json:"gloss"`
-	Phonetic string  `json:"phonetic"`
-	Example  string  `json:"example"`
-	DocID    *string `json:"doc_id"`
+	Word       string  `json:"word"`
+	Gloss      string  `json:"gloss"`
+	Definition string  `json:"definition"`
+	Phonetic   string  `json:"phonetic"`
+	Example    string  `json:"example"`
+	DocID      *string `json:"doc_id"`
 }
 
 // capture records a looked-up word. It's an idempotent upsert keyed on the word:
@@ -114,7 +120,11 @@ func (h *Handler) capture(w http.ResponseWriter, r *http.Request) {
 		errorJSON(w, http.StatusBadRequest, "invalid body")
 		return
 	}
-	word := strings.TrimSpace(req.Word)
+	// Normalize the same way the lexicon does (internal/lexicon: lower+trim) so
+	// the UNIQUE(user_id, word) upsert is genuinely idempotent — otherwise
+	// "Apple" at a sentence start and "apple" mid-line would create two separate
+	// cards on independent schedules.
+	word := strings.ToLower(strings.TrimSpace(req.Word))
 	if word == "" {
 		errorJSON(w, http.StatusBadRequest, "word is required")
 		return
@@ -124,14 +134,15 @@ func (h *Handler) capture(w http.ResponseWriter, r *http.Request) {
 	// schedule (due_at/reps/interval/ease) alone so re-looking-up a word never
 	// resets its progress.
 	_, err := h.DB.Exec(
-		`INSERT INTO vocab_words (user_id, word, gloss, phonetic, example, doc_id, due_at, interval_days)
-		 VALUES (?, ?, ?, ?, ?, ?, datetime('now', '+1 day'), 1)
+		`INSERT INTO vocab_words (user_id, word, gloss, definition, phonetic, example, doc_id, due_at, interval_days)
+		 VALUES (?, ?, ?, ?, ?, ?, ?, datetime('now', '+1 day'), 1)
 		 ON CONFLICT(user_id, word) DO UPDATE SET
-		   gloss    = excluded.gloss,
-		   phonetic = excluded.phonetic,
-		   example  = CASE WHEN excluded.example != '' THEN excluded.example ELSE vocab_words.example END,
-		   doc_id   = COALESCE(excluded.doc_id, vocab_words.doc_id)`,
-		db.LocalUserID, word, req.Gloss, req.Phonetic, req.Example, req.DocID,
+		   gloss      = excluded.gloss,
+		   definition = excluded.definition,
+		   phonetic   = excluded.phonetic,
+		   example    = CASE WHEN excluded.example != '' THEN excluded.example ELSE vocab_words.example END,
+		   doc_id     = COALESCE(excluded.doc_id, vocab_words.doc_id)`,
+		db.LocalUserID, word, req.Gloss, req.Definition, req.Phonetic, req.Example, req.DocID,
 	)
 	if err != nil {
 		serverError(w, err)