3.2 conversation depth: cross-intent anaphora + fact-by-key query

- session.go: add History []Turn + Turn type for multi-turn context
- slots.go: add AnaphoraResolver with Resolve() for RU pronoun detection
  (это/он/она/оно/тот/мой and inflected forms)
- followup.go: extend followUpMerge with cross-intent inheritance:
  Query/Fact/Reminder after a Fact with anaphora inherits the key.
  Same-intent path unchanged. Anaphora detection from utterance.
- voice.go: add fact-by-key lookup path in applyAction for IntentQuery
  when dialogue resolved an anaphoric reference (calls LatestFact,
  formats with formatTime helper). History tracked in Session.History
  capped at 4 most recent turns.
- followup_test.go: 7 new test cases: anaphora query-after-fact,
  no-inheritance-without-anaphora, three-turn break, anaphora in
  reminder, anaphora in fact, explicit key wins, time inheritance.
  make test green (303+, -race, all 29 packages).

internal/dialogue/session.go

@@ -27,11 +27,21 @@ type Slots struct {
 	HasFn   bool
 }
 
+// Turn represents one utterance in a multi-turn dialogue history.
+// Carried by Session.History for cross-intent reference and anaphora
+// resolution (a later turn's pronoun points to an earlier turn's entity).
+type Turn struct {
+	Intent Intent
+	Slots  Slots
+	Text   string // raw utterance
+}
+
 type Session struct {
 	Intent    Intent
 	Slots     Slots
 	Timestamp time.Time
 	TTL       time.Duration
+	History   []Turn // most recent turns, newest last; used for anaphora + cross-intent
 }
 
 func (s *Session) IsExpired(now time.Time) bool {

internal/router/slots.go

@@ -328,6 +328,41 @@ func parseDurationValue(s string) (string, bool) {
 	return strconv.Itoa(n) + unit, true
 }
 
+// AnaphoraResolver resolves pronouns like "это", "он", "она" to the prior
+// turn's key entity. Returns a (key, value) pair the prior fact carried,
+// or ("", "", false) when no pronoun is detected.
+type AnaphoraResolver struct{}
+
+// Resolve checks if text contains an anaphoric reference to a prior turn's
+// entity. For MVP this handles the common Russian pronouns:
+//   - "это" / "этого" / "этому" / "этим" / "этом" → "this" (most common)
+//   - "он" / "его" / "ему" / "ним" → "he/it", masc
+//   - "она" / "её" / "ей" / "ней" → "she/it", fem
+//   - "оно" → "it", neuter
+//
+// Returns the matching pronoun type for cross-referencing with prior slots.
+func (AnaphoraResolver) Resolve(text string) (ref string, ok bool) {
+	s := strings.ToLower(strings.TrimSpace(text))
+	toks := strings.Fields(s)
+	for _, tok := range toks {
+		switch tok {
+		case "это", "этого", "этому", "этим", "этом", "эти", "эта":
+			return "this", true
+		case "он", "его", "ему", "ним":
+			return "he", true
+		case "она", "её", "ей", "ней":
+			return "she", true
+		case "оно":
+			return "it", true
+		case "тот", "та", "то", "те":
+			return "that", true
+		case "мой", "моего", "моему", "моим", "моём", "моя", "моей", "моё":
+			return "mine", true
+		}
+	}
+	return "", false
+}
+
 // ParseCalendarDate detects RU calendar date words in text and returns the
 // resolved time (midnight UTC+0 for "сегодня"/"today", next day for "завтра"/"tomorrow").
 // Returns zero time + false if no match.