the simulator can script a chat reply (V-542)

Item 4. actionChat calls h.phraser.PhraseChat, and LLMPhraser posts raw
HTTP to /v1/chat/completions rather than going through the llm client
scriptedLLM stands in for. The simulator wired phraser.NewStub() anyway,
so no scenario could assert what she says on a chat turn: every reply came
back as a pick from fallbacks_ru_v1.json, four variants deep, and the same
scenario returned "тут я пас." one run and "не знаю, честно." the next.

scriptedPhraser embeds the Stub and overrides PhraseChat only, reading the
same script entries the router reads. A reply is accepted in either shape
the phrasing contract allows, the {"response","mood"} object or plain text,
so a scenario writes one thing for both paths.

An unscripted chat turn returns an error rather than a fallback, matching
scriptedLLM: actionChat logs it and uses ChatFallback(), so scenarios that
never meant to assert a chat reply behave as before.

conversation_anaphora turn 4 now pins its text — the reply that asks which
device he means, which is the recorded defect in the box's own words.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

cmd/mavend/simulator_test.go

@@ -347,6 +347,55 @@ func (s *scriptedLLM) Complete(_ context.Context, r llm.Req) (string, error) {
 		map[bool]string{true: "route", false: "reply"}[routing], truncateRunes(r.User, 60))
 }
 
+// scriptedPhraser answers the chat path from the same script the router reads.
+//
+// It exists because actionChat calls h.phraser.PhraseChat, and the production
+// implementation posts raw HTTP to /v1/chat/completions rather than going
+// through the llm client scriptedLLM stands in for. So until this, no scenario
+// could script what she SAYS on a chat turn: the simulator wired phraser.NewStub()
+// and every chat reply came back as a pick from fallbacks_ru_v1.json, four
+// variants deep, which varied between two runs of one scenario (V-542 item 4).
+//
+// Everything except PhraseChat is the Stub's, by embedding. A nudge and a
+// reminder are phrased by the tick loop, which has its own phraser and its own
+// assertions; this seam is only about the conversation.
+type scriptedPhraser struct {
+	*phraser.Stub
+	entries []scriptEntry
+}
+
+// PhraseChat returns the scripted reply for the utterance, or an error when the
+// scenario scripted none. The error rather than a fallback is deliberate and
+// matches scriptedLLM: actionChat logs it and falls back to ChatFallback(), so a
+// scenario that never meant to assert on a chat reply behaves exactly as it did
+// before, and one that DID means to is told its script has a hole.
+func (p *scriptedPhraser) PhraseChat(_ context.Context, utterance string, _ []dialogue.Turn) (string, error) {
+	for _, e := range p.entries {
+		if e.Reply == "" {
+			continue
+		}
+		if e.Match != "" && !strings.Contains(strings.ToLower(utterance), strings.ToLower(e.Match)) {
+			continue
+		}
+		return chatReplyText(e.Reply), nil
+	}
+	return "", fmt.Errorf("simulator: no scripted chat reply for %q", truncateRunes(utterance, 60))
+}
+
+// chatReplyText reads a scripted reply in either shape the phrasing contract
+// allows: the {"response","mood"} object the model emits, or plain text.
+// LLMPhraser does this parse itself, so a scenario writes one thing and both
+// paths understand it.
+func chatReplyText(reply string) string {
+	var out struct {
+		Response string `json:"response"`
+	}
+	if err := json.Unmarshal([]byte(reply), &out); err == nil && out.Response != "" {
+		return out.Response
+	}
+	return reply
+}
+
 // ---------------------------------------------------------------------------
 // Building the world
 // ---------------------------------------------------------------------------
@@ -440,7 +489,7 @@ func newSimWorld(t *testing.T, sc scenario) *simWorld {
 		api:                api,
 		matcher:            matcher,
 		tools:              tool.NewExecutor(api, 5*time.Second),
-		phraser:            phraser.NewStub(),
+		phraser:            &scriptedPhraser{Stub: phraser.NewStub(), entries: sc.Script},
 		replier:            newLLMReplier(scripted, nil),
 		now:                clock.Now,
 		dataStore:          st,