store, mavend: a fact is indexed as the fact, not as the utterance (V-493)

queryMemory returns a fact's stored text verbatim, so the text the write path
indexed is what he hears. It was the utterance, which made recall of any
voice-tapped fact answer with the sentence he said: go_version = 1.20 was
indexed as "какая последняя версия языка Go?", and that question came back.

FactRecallText renders the fact instead, and the utterance stays in meta as
provenance. Correcting a value now drops the key's vectors the way voiding one
does, since the superseded value was still answering.

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

internal/store/facts.go

@@ -47,6 +47,39 @@ func (s *Store) WriteFact(ctx context.Context, ts time.Time, kind FactKind, key,
 	return id, nil
 }
 
+// FactRecallText is the text a fact is indexed under and read back as (#493).
+//
+// It used to be the utterance that wrote the fact, so recall of ANY
+// voice-tapped fact answered with the sentence he said instead of the value
+// stored: `go_version = 1.20` was indexed as "какая последняя версия языка
+// Go?", and that question is what came back. The poisoned rows made the defect
+// visible; the shape was wrong for legitimate facts too.
+//
+// The key is spoken with its underscores dropped, because a key is written for
+// the store and this string is read out loud.
+func FactRecallText(key, value string) string {
+	spoken := strings.TrimSpace(strings.ReplaceAll(key, "_", " "))
+	v := strings.TrimSpace(DecodeFactValue(value))
+	switch {
+	case v == "":
+		return spoken
+	case spoken == "":
+		return v
+	}
+	return spoken + " — " + v
+}
+
+// DecodeFactValue unwraps a stored value for reading. The column holds raw json
+// when the writer serialized one (SetValue, CorrectValue) and a plain string
+// when it did not (a voice tap), so a reader that wants the text handles both.
+func DecodeFactValue(value string) string {
+	var s string
+	if err := json.Unmarshal([]byte(value), &s); err == nil {
+		return s
+	}
+	return value
+}
+
 // LatestFact returns the latest non-voided fact for key, or ErrNoFact.
 // "Non-voided" = no later row has voids_id pointing at it. We resolve this by
 // taking the newest row whose id is not referenced by any voids_id.
@@ -291,6 +324,20 @@ func (s *Store) CorrectValue(ctx context.Context, key, source string, value any,
 	if err != nil {
 		return 0, fmt.Errorf("last insert id: %w", err)
 	}
+	// The same repair a void needs, for the same reason (#493). A correction
+	// supersedes the value, and the vector still holds the old one, so recall
+	// kept answering with the value he had just corrected. Dropping it costs
+	// the key its recall vector until the fact is tapped again: this layer has
+	// no embedder, and a missing vector loses a question while a stale one
+	// answers it wrongly.
+	//
+	// Best-effort: the corrected row is committed, and a correction that lands
+	// beats one that fails on cleanup.
+	if n, derr := s.VectorMemory().DeletePrefix(ctx, "fact:"+key+":"); derr != nil {
+		log.Printf("store: correct %q: memory vectors survive: %v", key, derr)
+	} else if n > 0 {
+		log.Printf("store: correct %q: dropped %d superseded memory vector(s)", key, n)
+	}
 	return newID, nil
 }