Add the pending-question data layer for slot clarification

PendingQuestion plus ClarifyStore: same shape, locking and expiry as SessionStore. Answer fills only the missing slots and never overwrites a filled one. No wiring yet — TODOs mark the daemon hooks.
Reviewer: MaxAttempts is 1 on purpose (Maven asks once, she is not a nag).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CGeSZxh1DCtRxmFVSYVGvJ

internal/dialogue/clarify.go

@@ -0,0 +1,171 @@
+package dialogue
+
+import (
+	"sync"
+	"time"
+)
+
+// Slot names one field of Slots. Named type, not a free string, so a missing
+// slot cannot be misspelled — the question phrasing switches on these.
+type Slot string
+
+const (
+	SlotTime  Slot = "time"  // Slots.Time / HasTime
+	SlotKey   Slot = "key"   // Slots.Key / HasKey
+	SlotValue Slot = "value" // Slots.Value (paired with Key)
+	SlotFn    Slot = "fn"    // Slots.Fn / HasFn
+	SlotText  Slot = "text"  // Slots.Text
+)
+
+// MaxAttempts is 1 because Maven is not a nag (DESIGN.md § Non-goals). She asks
+// one clarifying question. If the answer still leaves the slot empty she drops
+// the request instead of asking again.
+const MaxAttempts = 1
+
+// PendingQuestion is what Maven holds while she waits for an answer to an open
+// question. Unlike the yes/no confirms in cmd/mavend/voice.go, the answer here
+// is free text that fills a missing slot rather than a verdict.
+type PendingQuestion struct {
+	Intent    Intent // what the router already guessed
+	Slots     Slots  // what it already filled
+	Missing   []Slot // what is still empty, in the order to ask about
+	Utterance string // the user's original raw words
+	Asked     time.Time
+	TTL       time.Duration
+	Attempts  int // questions already asked; capped by MaxAttempts
+}
+
+func (q *PendingQuestion) IsExpired(now time.Time) bool {
+	return now.After(q.Asked.Add(q.TTL))
+}
+
+// CanAsk reports whether Maven may ask another question about this request.
+func (q *PendingQuestion) CanAsk() bool {
+	return q.Attempts < MaxAttempts
+}
+
+// TODO: the daemon will phrase the question text from Missing (one short ru
+// question per Slot, feminine self-reference) and speak it here.
+
+// ClarifyStore holds the parked questions. Same shape and locking as
+// SessionStore: keyed by dialogue id, expired entries dropped on read.
+type ClarifyStore struct {
+	mu         sync.RWMutex
+	questions  map[string]*PendingQuestion
+	defaultTTL time.Duration
+}
+
+func NewClarifyStore(defaultTTL time.Duration) *ClarifyStore {
+	if defaultTTL <= 0 {
+		// Short, like confirmTTL in voice.go: a clarifying question is a
+		// same-breath gesture, a stale one should not eat a later utterance.
+		defaultTTL = 90 * time.Second
+	}
+	return &ClarifyStore{
+		questions:  make(map[string]*PendingQuestion),
+		defaultTTL: defaultTTL,
+	}
+}
+
+// TODO: the daemon will Put a question here when Decision.Clarify fires, in
+// place of the flat "не разобрала" reply (cmd/mavend/voice.go).
+func (s *ClarifyStore) Put(id string, q *PendingQuestion) {
+	if q.TTL <= 0 {
+		q.TTL = s.defaultTTL
+	}
+	s.mu.Lock()
+	s.questions[id] = q
+	s.mu.Unlock()
+}
+
+// TODO: the daemon will Get on the next turn, parse that turn into Slots, call
+// Answer, and Delete — the open-question twin of resolveConfirm.
+func (s *ClarifyStore) Get(id string, now time.Time) *PendingQuestion {
+	s.mu.RLock()
+	q, ok := s.questions[id]
+	s.mu.RUnlock()
+	if !ok {
+		return nil
+	}
+	if q.IsExpired(now) {
+		s.Delete(id)
+		return nil
+	}
+	return q
+}
+
+func (s *ClarifyStore) Delete(id string) {
+	s.mu.Lock()
+	delete(s.questions, id)
+	s.mu.Unlock()
+}
+
+// Answer merges the slots parsed from the user's answer into the parked ones.
+// Only the slots listed in Missing are filled, and an already filled slot is
+// never overwritten — the answer completes the original request, it does not
+// restate it. Parsing the answer text into `answer` is the caller's job; this
+// package must stay free of internal/router.
+func (q *PendingQuestion) Answer(text string, answer Slots) Slots {
+	out := q.Slots
+	for _, slot := range q.Missing {
+		switch slot {
+		case SlotTime:
+			if !out.HasTime && answer.HasTime {
+				out.Time = answer.Time
+				out.HasTime = true
+			}
+		case SlotKey:
+			if !out.HasKey && answer.HasKey {
+				out.Key = answer.Key
+				out.HasKey = true
+			}
+		case SlotValue:
+			if out.Value == "" && answer.Value != "" {
+				out.Value = answer.Value
+			}
+		case SlotFn:
+			if !out.HasFn && answer.HasFn {
+				out.Fn = answer.Fn
+				out.HasFn = true
+				if len(out.Args) == 0 {
+					out.Args = append([]string(nil), answer.Args...)
+				}
+			}
+		case SlotText:
+			if out.Text == "" {
+				if answer.Text != "" {
+					out.Text = answer.Text
+				} else {
+					// No parse for a text slot — the raw answer IS the text.
+					out.Text = text
+				}
+			}
+		}
+	}
+	return out
+}
+
+// StillMissing lists the slots that are empty in s, out of the ones asked for.
+// The caller uses it to decide between acting and dropping the request.
+func StillMissing(want []Slot, s Slots) []Slot {
+	var out []Slot
+	for _, slot := range want {
+		empty := false
+		switch slot {
+		case SlotTime:
+			empty = !s.HasTime
+		case SlotKey:
+			empty = !s.HasKey
+		case SlotValue:
+			empty = s.Value == ""
+		case SlotFn:
+			empty = !s.HasFn
+		case SlotText:
+			empty = s.Text == ""
+		}
+		if empty {
+			out = append(out, slot)
+		}
+	}
+	return out
+}