The garden learns which language a card is in, and read-aloud stops guessing

Phase 28 (c), the last of the phase. A word met inside a Portuguese
document is a Portuguese card: migration 0018 mirrors documents.doc_lang
onto vocab_words, set server-side from the ownership lookup capture was
already making. Every card still reviews — filtering the queue to the
half she is learning would drop the words she actually met.

Read-aloud was the larger surprise. detectLang routed Han/kana to
Chinese and everything else to en-US, so the zh pair was accidentally
right and every Latin pair wrong. doc_lang now reaches the client
read-only on the document JSON, and docLang(text, verdict) answers for a
passage taken out of it — with the script test still winning, because
quoted Chinese must never be spelled out one "Chinese letter" at a time.

Claude-Session: https://claude.ai/code/session_01GJHNvirh7Hzhc9RL3HAvz7

internal/docs/handlers.go

@@ -225,13 +225,14 @@ func (h *Handler) fetch(userID, id string) (db.Document, error) {
 	var doc db.Document
 	err := h.DB.QueryRow(
 		`SELECT id, user_id, title, content, content_text, tone, word_count,
-		        created_at, updated_at, preserve_history
+		        created_at, updated_at, preserve_history, doc_lang
 		   FROM documents
 		  WHERE id = ? AND user_id = ?`,
 		id, userID,
 	).Scan(
 		&doc.ID, &doc.UserID, &doc.Title, &doc.Content, &doc.ContentText,
 		&doc.Tone, &doc.WordCount, &doc.CreatedAt, &doc.UpdatedAt, &doc.PreserveHistory,
+		&doc.DocLang,
 	)
 	return doc, err
 }