mavend, eval: use the phrasing errors the phraser now returns (V-397)

Call sites take the fallback text and log the error instead of treating a
canned string as success. phraseSource drops the text entirely — its callers
hold the passage and read it back better than "вот что я нашла: <passage>".

The talk scorer's before-and-after model probe (the #395 workaround) goes;
the run now fails only when every case errored, which is the honest
"nothing was measured" condition. TalkFixture gets its own schema version so
the two fixtures can be versioned apart.

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

cmd/mavend/worldmodel.go

@@ -54,7 +54,11 @@ func (h *reactiveHandler) phraseSource(ctx context.Context, name, utterance stri
 		log.Printf("voice: %s: no world model, reading the source back instead", name)
 		return ""
 	case err != nil:
+		// The resident phraser answers this call with its fallback text and the
+		// error together. Drop the text: these callers hold the passage itself
+		// and read it back better than "вот что я нашла: <passage>" does.
 		log.Printf("voice: %s: phrase: %v", name, err)
+		return ""
 	}
 	return reply
 }