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'));
 `,
 		},
 	}

internal/db/models.go

@@ -34,15 +34,20 @@ type User struct {
 // (source of truth for the editor); `ContentText` is the flattened plain text
 // kept in sync on every save and fed to the LLM.
 type Document struct {
-	ID          string    `json:"id"`
-	UserID      string    `json:"user_id"`
-	Title       string    `json:"title"`
-	Content     string    `json:"content"`      // Tiptap JSON
-	ContentText string    `json:"content_text"` // plain text for the LLM
-	Tone        string    `json:"tone"`         // target writing tone; steers LLM advice
-	WordCount   int       `json:"word_count"`
-	CreatedAt   time.Time `json:"created_at"`
-	UpdatedAt   time.Time `json:"updated_at"`
+	ID          string `json:"id"`
+	UserID      string `json:"user_id"`
+	Title       string `json:"title"`
+	Content     string `json:"content"`      // Tiptap JSON
+	ContentText string `json:"content_text"` // plain text for the LLM
+	Tone        string `json:"tone"`         // target writing tone; steers LLM advice
+	WordCount   int    `json:"word_count"`
+	// DocLang is which language this document is written in — '' | 'en' | 'pair'
+	// (migration 0017), written by the checkpoint pass and never by the client.
+	// It reaches the client read-only, for the one decision the client has to
+	// make on its own: which voice reads a selection aloud. '' means English.
+	DocLang   string    `json:"doc_lang"`
+	CreatedAt time.Time `json:"created_at"`
+	UpdatedAt time.Time `json:"updated_at"`
 
 	// PreserveHistory opts this document out of auto-snapshot pruning so its
 	// full writing trail survives as authorship evidence (see the passport).
@@ -110,15 +115,15 @@ const (
 // coordinates at render time (spec Note #6). `Replacement` is empty for `voice`
 // flags — those are awareness-only, with no correction to apply.
 type Suggestion struct {
-	ID          string    `json:"id"`
-	DocID       string    `json:"doc_id"`
-	FromPos     int       `json:"from_pos"`
-	ToPos       int       `json:"to_pos"`
-	Original    string    `json:"original"`
-	Replacement string    `json:"replacement"`
-	Explanation string    `json:"explanation"`
-	Type        string    `json:"type"`   // grammar | phrasing | idiom | clarity | translate | voice | collocation
-	Status      string    `json:"status"` // pending | accepted | rejected
+	ID          string `json:"id"`
+	DocID       string `json:"doc_id"`
+	FromPos     int    `json:"from_pos"`
+	ToPos       int    `json:"to_pos"`
+	Original    string `json:"original"`
+	Replacement string `json:"replacement"`
+	Explanation string `json:"explanation"`
+	Type        string `json:"type"`   // grammar | phrasing | idiom | clarity | translate | voice | collocation
+	Status      string `json:"status"` // pending | accepted | rejected
 	// Source names the engine that proposed the edit, not its family: an offline
 	// rule and the model can both propose a collocation, and the writer is never
 	// told which one spoke. It exists so each pass can replace its own rows.
@@ -128,10 +133,10 @@ type Suggestion struct {
 
 // Suggestion type and status values, mirrored from the schema CHECK constraints.
 const (
-	SuggestionTypeGrammar     = "grammar"
-	SuggestionTypePhrasing    = "phrasing"
-	SuggestionTypeIdiom       = "idiom"
-	SuggestionTypeClarity     = "clarity"
+	SuggestionTypeGrammar  = "grammar"
+	SuggestionTypePhrasing = "phrasing"
+	SuggestionTypeIdiom    = "idiom"
+	SuggestionTypeClarity  = "clarity"
 	// A span she wrote in her own language, rendered into English. Not a
 	// correction — nothing was wrong with it — which is why it is its own type
 	// rather than a clarity fix: the card is the pair model's flagship moment