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/db/db.go

@@ -613,6 +613,31 @@ ALTER TABLE users ADD COLUMN direction TEXT NOT NULL DEFAULT 'learning_en'
 			stmt: `
 ALTER TABLE documents ADD COLUMN doc_lang TEXT NOT NULL DEFAULT ''
     CHECK(doc_lang IN ('', 'en', 'pair'));
+`,
+		},
+		{
+			// Which language a garden card is in — the same '' | 'en' | 'pair'
+			// vocabulary as documents.doc_lang, and set from it: a word is captured
+			// (or a phrase planted) out of a document, so the document's verdict is
+			// the card's language. A card with no document keeps '', which reads as
+			// English like every other empty here.
+			//
+			// The garden needed this the moment a document could be written in her
+			// own language. Before Phase 28 every card was English by construction;
+			// now a Portuguese lookup lands beside an English one with nothing to
+			// tell them apart, and two surfaces get it wrong without the tag — the
+			// review card's read-aloud (which would say a Portuguese word in a US
+			// English voice) and the panel, where a mixed garden is illegible.
+			//
+			// Every card is reviewed regardless. Filtering the queue to the half she
+			// is learning was the alternative and is wrong for the writer this is
+			// for: the words she met while writing Portuguese are still words she
+			// met, and a garden that quietly drops them is a garden that stops being
+			// a record of her reading.
+			name: "0018_vocab_lang",
+			stmt: `
+ALTER TABLE vocab_words ADD COLUMN lang TEXT NOT NULL DEFAULT ''
+    CHECK(lang IN ('', 'en', 'pair'));
 `,
 		},
 	}