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/suggestions/plant_test.go

@@ -184,3 +184,60 @@ func TestCorrectedSentence(t *testing.T) {
 		t.Errorf("unterminated doc: got %q", got)
 	}
 }
+
+// TestPlantedPhraseCarriesTheDocumentLanguage: a chunk planted out of a document
+// written in her own language is a card in that language. The collocation pass
+// itself deliberately did not flip in Phase 28 — its prompt is per-language
+// knowledge, not framing — but the phrase it hands over is still lifted from her
+// prose, so the card has to know what language that prose was in or the garden
+// will read it aloud in the wrong voice.
+func TestPlantedPhraseCarriesTheDocumentLanguage(t *testing.T) {
+	srv, docID, h := newTestServer(t, &stubClient{})
+	if _, err := h.DB.Exec(`UPDATE documents SET doc_lang = 'pair' WHERE id = ?`, docID); err != nil {
+		t.Fatalf("set doc_lang: %v", err)
+	}
+	id := seedSuggestion(t, h, docID,
+		"Ontem foi difícil. Tive de tomar uma decisão sobre o trabalho.",
+		db.SuggestionTypeCollocation, "tomar uma decisão", "tomar uma decisão",
+		"Em português diz-se “tomar” uma decisão.")
+
+	if rec := do(t, srv, http.MethodPost, "/suggestions/"+id+"/accept", ""); rec.Code != http.StatusNoContent {
+		t.Fatalf("accept: got %d, want 204", rec.Code)
+	}
+
+	var lang string
+	if err := h.DB.QueryRow(
+		`SELECT lang FROM vocab_words WHERE user_id = ? AND word = ?`,
+		db.LocalUserID, "tomar uma decisão",
+	).Scan(&lang); err != nil {
+		t.Fatalf("read planted card: %v", err)
+	}
+	if lang != "pair" {
+		t.Fatalf("planted card lang = %q, want pair", lang)
+	}
+}
+
+// TestPlantedPhraseOnAnEnglishDocumentIsUnchanged is the other half, and the one
+// every account is on today: an English document plants an English card, and the
+// empty backfill and 'en' both mean that.
+func TestPlantedPhraseOnAnEnglishDocumentIsUnchanged(t *testing.T) {
+	srv, docID, h := newTestServer(t, &stubClient{})
+	id := seedSuggestion(t, h, docID, "I had to do a decision about the job.",
+		db.SuggestionTypeCollocation, "do a decision", "make a decision",
+		"English pairs “make” with “decision”.")
+
+	if rec := do(t, srv, http.MethodPost, "/suggestions/"+id+"/accept", ""); rec.Code != http.StatusNoContent {
+		t.Fatalf("accept: got %d, want 204", rec.Code)
+	}
+
+	var lang string
+	if err := h.DB.QueryRow(
+		`SELECT lang FROM vocab_words WHERE user_id = ? AND word = ?`,
+		db.LocalUserID, "make a decision",
+	).Scan(&lang); err != nil {
+		t.Fatalf("read planted card: %v", err)
+	}
+	if lang == "pair" {
+		t.Fatalf("planted card lang = %q on an English document, want en or empty", lang)
+	}
+}