feat: add conversation with grounded replies, sample mind and M1 acceptance test

Phase 8, completing milestone M1. A user message is stored and appended
as an observation event carrying trust, actor, channel and reference. The
perceive process analyses it deterministically (intent, introspection
kind, entities, claims, urgency) and, within the per-cycle model
allowance, enriches it through the perceive prompt. Its handler writes a
perception event, an episodic memory with participants, turns claims into
beliefs whose evidence is the message, and builds a response intent from
state: beliefs and memories for the topic, evidence rows for why-questions,
the uncertain band, contested beliefs and their links, recent learning,
status changes, and honest declines for subsystems that do not exist yet
or for requests with no capabilities. The respond prompt phrases the
intent when a model is assigned; otherwise the reply is a direct
rendering of the intent. response_generated cites the message, the
perception, every belief and memory used, the episode and the model call.

API: conversations, messages with optional wait, one-shot ask; chat UI
with live refresh and a per-reply intent view. Sample mind Dani as a
strictly decoded seed document with an import endpoint and noemactl mind
import. tests/m1 drives all fourteen milestone steps including restart.

internal/beliefs/store.go

@@ -787,3 +787,94 @@ func trunc(s string, n int) string {
 	}
 	return s
 }
+
+// Search returns live beliefs matching any of the words in text, best match
+// first. Used to answer "what do you believe about X".
+func (s *Store) Search(ctx context.Context, mind ids.ID, text string, limit int) ([]Belief, error) {
+	toks, _ := Polarity(text)
+	if len(toks) == 0 {
+		return nil, nil
+	}
+	if limit <= 0 || limit > 50 {
+		limit = 10
+	}
+	q := strings.Join(toks, " | ")
+	rows, err := s.db.Query(ctx, `SELECT `+cols+` FROM beliefs b WHERE b.mind_id=$1 AND b.status NOT IN ('superseded') AND b.search @@ to_tsquery('english', $2)
+		ORDER BY ts_rank_cd(b.search, to_tsquery('english', $2)) DESC, b.confidence DESC LIMIT $3`, mind, q, limit)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []Belief
+	for rows.Next() {
+		b, err := scan(rows)
+		if err != nil {
+			return nil, err
+		}
+		out = append(out, b)
+	}
+	return out, rows.Err()
+}
+
+// Change describes a belief whose status or confidence moved.
+type Change struct {
+	Belief     Belief    `json:"belief"`
+	FromStatus Status    `json:"from_status"`
+	FromConf   float64   `json:"from_confidence"`
+	Reason     string    `json:"reason"`
+	At         time.Time `json:"at"`
+}
+
+// RecentChanges lists beliefs whose latest version differs in status from an
+// earlier version within the window ("what have you changed your mind about").
+func (s *Store) RecentChanges(ctx context.Context, mind ids.ID, since time.Time, limit int) ([]Change, error) {
+	if limit <= 0 || limit > 50 {
+		limit = 10
+	}
+	rows, err := s.db.Query(ctx, `WITH latest AS (
+			SELECT DISTINCT ON (belief_id) belief_id, status, confidence, reason, created_at FROM belief_versions WHERE mind_id=$1 AND created_at >= $2 ORDER BY belief_id, version DESC),
+		first AS (
+			SELECT DISTINCT ON (belief_id) belief_id, status, confidence FROM belief_versions WHERE mind_id=$1 ORDER BY belief_id, version ASC)
+		SELECT `+cols+`, f.status, f.confidence, l.reason, l.created_at FROM latest l JOIN first f ON f.belief_id=l.belief_id JOIN beliefs b ON b.id=l.belief_id
+		WHERE l.status <> f.status ORDER BY l.created_at DESC LIMIT $3`, mind, since, limit)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []Change
+	for rows.Next() {
+		var c Change
+		var epi, status, fromStatus string
+		var detail []byte
+		var origin, superseded, pinned *string
+		b := &c.Belief
+		if err := rows.Scan(&b.ID, &b.MindID, &b.Proposition, &b.Subject, &epi, &status, &b.Confidence, &b.Prior, &b.Version, &b.Source, &detail, &origin, &superseded, &pinned, &b.FirstCreated, &b.LastEvaluated, &b.Evaluations, &fromStatus, &c.FromConf, &c.Reason, &c.At); err != nil {
+			return nil, err
+		}
+		b.Epistemic, b.Status, c.FromStatus = concepts.Epistemic(epi), Status(status), Status(fromStatus)
+		out = append(out, c)
+	}
+	return out, rows.Err()
+}
+
+// Uncertain returns beliefs in the middle band or contested, least certain first.
+func (s *Store) Uncertain(ctx context.Context, mind ids.ID, limit int) ([]Belief, error) {
+	if limit <= 0 || limit > 50 {
+		limit = 10
+	}
+	rows, err := s.db.Query(ctx, `SELECT `+cols+` FROM beliefs b WHERE b.mind_id=$1 AND b.status NOT IN ('rejected','superseded') AND (b.status='contested' OR (b.confidence BETWEEN 0.3 AND 0.7))
+		ORDER BY abs(b.confidence-0.5) ASC, b.last_evaluated DESC LIMIT $2`, mind, limit)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []Belief
+	for rows.Next() {
+		b, err := scan(rows)
+		if err != nil {
+			return nil, err
+		}
+		out = append(out, b)
+	}
+	return out, rows.Err()
+}