feat: LLM router with chat intent and Cyrillic wake-word support

- Add LLMRouter: grammar-constrained LFM call for intent classification
  after stage-0, before classifier cascade. Errors fall through gracefully.
- Add IntentChat: conversational intent with no store side-effect, routed
  through LLM -> phraser chat endpoint.
- Extract slots for Chat: no structured slots, full utterance is payload.
- Extend stage-0 grammars to fire through Cyrillic wake-word spellings
  (Мэйвен/Мейвен/Майвен/etc.) produced by Russian STT model.
- StripWakeToken helper strips leading wake in any script so time/date
  grammars still match when wake is present.
- Add classifier examples for chat utterances (EN + RU).
- Wire LLMRouter into Router.Config; optional, nil-safe.

internal/router/router_test.go

@@ -19,6 +19,7 @@ func seedClassifier(t *testing.T, c *Classifier) {
 	facts := []string{"drank water", "i drank water", "ate lunch", "slept six hours", "had a meal"}
 	notes := []string{"gpu driver fixed the flicker", "prefer backups at three am", "note that the router reboots on tuesday"}
 	queries := []string{"is the backup up", "when did i last eat", "is nginx running", "how much water today"}
+	chats := []string{"what do you think about", "tell me something interesting", "how are you", "расскажи что-нибудь", "что ты думаешь", "как дела"}
 	for _, x := range acts {
 		if err := c.AddExample(ctx, IntentAct, x); err != nil {
 			t.Fatalf("seed act %q: %v", x, err)
@@ -44,6 +45,11 @@ func seedClassifier(t *testing.T, c *Classifier) {
 			t.Fatalf("seed query %q: %v", x, err)
 		}
 	}
+	for _, x := range chats {
+		if err := c.AddExample(ctx, IntentChat, x); err != nil {
+			t.Fatalf("seed chat %q: %v", x, err)
+		}
+	}
 }
 
 func newTestRouter(t *testing.T, threshold float64) *Router {
@@ -97,6 +103,24 @@ func TestStage0WakeWordFallsThroughOnUnknownAct(t *testing.T) {
 	}
 }
 
+func TestStage0GrammarFiresThroughCyrillicWakeWord(t *testing.T) {
+	// The STT is a Russian model — it transcribes the spoken wake word
+	// phonetically ("Мэйвен"), never as the Latin "maven". Grammars that
+	// don't expect a wake prefix (time/date) must still fire when one is
+	// there, otherwise these fall through to the classifier and get
+	// misrouted into IntentReminder (see stage0.go's wakeToken comment).
+	r := newTestRouter(t, 0.0)
+	r.grammars = append(r.grammars, SystemTimeDateGrammars()...)
+
+	d, err := r.Route(context.Background(), "Мэйвен который час", refNow())
+	if err != nil {
+		t.Fatalf("route: %v", err)
+	}
+	if d.Stage != 0 || d.Intent != IntentSystem {
+		t.Fatalf("want stage0 system, got %+v", d)
+	}
+}
+
 // ----------------------------- stage 1 ---------------------------------------
 
 func TestStage1ClassifiesAct(t *testing.T) {
@@ -300,6 +324,28 @@ func TestClassifierDeterministicOrdering(t *testing.T) {
 	}
 }
 
+func TestStage1ClassifiesChat(t *testing.T) {
+	r := newTestRouter(t, 0.0)
+	cases := []struct {
+		in   string
+		want Intent
+	}{
+		{"what do you think about ai", IntentChat},
+		{"tell me something interesting", IntentChat},
+		{"как дела", IntentChat},
+		{"расскажи что-нибудь", IntentChat},
+	}
+	for _, c := range cases {
+		d, err := r.Route(context.Background(), c.in, refNow())
+		if err != nil {
+			t.Fatalf("route %q: %v", c.in, err)
+		}
+		if d.Intent != c.want {
+			t.Errorf("%q: want %s, got %s (conf %f)", c.in, c.want, d.Intent, d.Confidence)
+		}
+	}
+}
+
 func TestClassifierIntentsSorted(t *testing.T) {
 	emb := NewHashEmbedder(32)
 	c := NewClassifier(emb)