fix: the slots converter was still dropping the fact Value (V-365)

dialogue.Slots gained Value in 925ce22, but toDialogueSlots never copied
it, so a clarifying answer carrying a fact payload still landed nowhere:
clarify.go:202 sends the answer through the converter, and the SlotValue
arm reads answer.Value.

Both converters now carry every field. TestSlotsParity compares the two
field sets by name and type; TestSlotsRoundTrip populates every router
field and checks the round trip, and fails the fixture itself when a new
field is left zero.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QChoBS5qJSrCV98oNUnHNU

cmd/mavend/followup.go

@@ -12,13 +12,21 @@ import (
 // which waits on voice-print attribution (see PROGRESS multi-user deferral).
 const voiceDialogueID = "voice"
 
-// toDialogueSlots projects the router's slots onto the dialogue layer's subset
-// (everything except the fact Value, which the dialogue layer doesn't carry).
+// toDialogueSlots and applyDialogueSlots are the only bridge between
+// router.Slots and dialogue.Slots. dialogue must not import router (import
+// cycle), so the two structs are hand-kept copies and every field has to be
+// carried by hand here. Adding a field to either struct without adding it to
+// BOTH functions loses a slot silently — nothing fails to build. The tests in
+// slotsparity_test.go fail when the field sets or the converters stop matching;
+// when they do, fix these two functions, not the tests.
+
+// toDialogueSlots projects the router's slots onto the dialogue layer's copy.
 func toDialogueSlots(s router.Slots) dialogue.Slots {
 	return dialogue.Slots{
 		Time:    s.Time,
 		HasTime: s.HasTime,
 		Key:     s.Key,
+		Value:   s.Value,
 		HasKey:  s.HasKey,
 		Text:    s.Text,
 		Fn:      s.Fn,
@@ -27,11 +35,10 @@ func toDialogueSlots(s router.Slots) dialogue.Slots {
 	}
 }
 
-// applyDialogueSlots writes inherited dialogue slots back onto router slots,
-// preserving router-only fields (Value) the dialogue layer never touched.
+// applyDialogueSlots writes dialogue slots back onto router slots.
 func applyDialogueSlots(base router.Slots, d dialogue.Slots) router.Slots {
 	base.Time, base.HasTime = d.Time, d.HasTime
-	base.Key, base.HasKey = d.Key, d.HasKey
+	base.Key, base.Value, base.HasKey = d.Key, d.Value, d.HasKey
 	base.Text = d.Text
 	base.Fn, base.Args, base.HasFn = d.Fn, d.Args, d.HasFn
 	return base

cmd/mavend/slotsparity_test.go

@@ -0,0 +1,71 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/kami/maven/internal/dialogue"
+	"github.com/kami/maven/internal/router"
+)
+
+// TestSlotsParity — dialogue.Slots is a hand-kept copy of router.Slots
+// (dialogue must not import router: import cycle). Drift is silent, so this
+// test compares the two field sets by name and type. If it fails, add the new
+// field to both structs AND to toDialogueSlots/applyDialogueSlots in
+// followup.go — do not relax the test.
+func TestSlotsParity(t *testing.T) {
+	fields := func(v any) map[string]string {
+		rt := reflect.TypeOf(v)
+		out := make(map[string]string, rt.NumField())
+		for i := 0; i < rt.NumField(); i++ {
+			f := rt.Field(i)
+			out[f.Name] = f.Type.String()
+		}
+		return out
+	}
+	rf, df := fields(router.Slots{}), fields(dialogue.Slots{})
+	for name, typ := range rf {
+		dt, ok := df[name]
+		if !ok {
+			t.Errorf("router.Slots.%s (%s) missing from dialogue.Slots", name, typ)
+			continue
+		}
+		if dt != typ {
+			t.Errorf("field %s: router has %s, dialogue has %s", name, typ, dt)
+		}
+	}
+	for name, typ := range df {
+		if _, ok := rf[name]; !ok {
+			t.Errorf("dialogue.Slots.%s (%s) missing from router.Slots", name, typ)
+		}
+	}
+}
+
+// TestSlotsRoundTrip — the converters carry every field. A field the parity
+// test accepts can still be dropped in transit, so round-trip a fully
+// populated value and compare.
+func TestSlotsRoundTrip(t *testing.T) {
+	full := router.Slots{
+		Time:    time.Date(2026, 8, 2, 11, 0, 0, 0, time.UTC),
+		HasTime: true,
+		Fn:      "restart",
+		Args:    []string{"nginx"},
+		HasFn:   true,
+		Key:     "water",
+		Value:   `"drank"`,
+		HasKey:  true,
+		Text:    "выпил воды",
+	}
+	// Every field must be non-zero, or the round-trip proves nothing.
+	rv := reflect.ValueOf(full)
+	for i := 0; i < rv.NumField(); i++ {
+		if rv.Field(i).IsZero() {
+			t.Fatalf("field %s is zero: extend this fixture so the round-trip covers it",
+				rv.Type().Field(i).Name)
+		}
+	}
+	if got := applyDialogueSlots(router.Slots{}, toDialogueSlots(full)); !reflect.DeepEqual(got, full) {
+		t.Errorf("round-trip lost a slot:\n got %+v\nwant %+v", got, full)
+	}
+}