fix: unify trust tier labels in scoreboard dump API

internal/api/scoreboard_dump_test.go

@@ -55,6 +55,9 @@ func TestScoreboardDump_Handler(t *testing.T) {
 	if result.Rigs[0].Handle != "alice" {
 		t.Errorf("rig handle = %q, want alice", result.Rigs[0].Handle)
 	}
+	if result.Rigs[0].TrustTier != "newcomer" {
+		t.Errorf("rig trust_tier = %q, want newcomer (1 root stamp = weight 5)", result.Rigs[0].TrustTier)
+	}
 	if len(result.Stamps) != 1 {
 		t.Errorf("stamps count = %d, want 1", len(result.Stamps))
 	}

internal/commons/scoreboard_dump.go

@@ -11,6 +11,7 @@ type RigRow struct {
 	DisplayName  string `json:"display_name,omitempty"`
 	DolthubOrg   string `json:"dolthub_org,omitempty"`
 	TrustLevel   int    `json:"trust_level"`
+	TrustTier    string `json:"trust_tier"`
 	RegisteredAt string `json:"registered_at,omitempty"`
 	LastSeen     string `json:"last_seen,omitempty"`
 	RigType      string `json:"rig_type,omitempty"`
@@ -100,9 +101,34 @@ func QueryScoreboardDump(db DB) (*ScoreboardDump, error) {
 		return nil, fmt.Errorf("dumping badges: %w", err)
 	}
 
+	// Derive trust_tier for each rig from stamp weighted scores.
+	populateDumpTrustTiers(dump)
+
 	return dump, nil
 }
 
+// populateDumpTrustTiers computes weighted scores from stamps and sets
+// TrustTier on each RigRow, ensuring the dump uses the same tier labels
+// as the scoreboard API.
+func populateDumpTrustTiers(dump *ScoreboardDump) {
+	scores := make(map[string]int)
+	for _, s := range dump.Stamps {
+		weight := 0
+		switch s.Severity {
+		case "root":
+			weight = 5
+		case "branch":
+			weight = 3
+		case "leaf":
+			weight = 1
+		}
+		scores[s.Subject] += weight
+	}
+	for i := range dump.Rigs {
+		dump.Rigs[i].TrustTier = DeriveTrustTier(scores[dump.Rigs[i].Handle])
+	}
+}
+
 func queryDumpRigs(db DB) ([]RigRow, error) {
 	query := `SELECT handle, COALESCE(display_name,'') AS display_name, COALESCE(dolthub_org,'') AS dolthub_org,
   COALESCE(trust_level,0) AS trust_level, COALESCE(registered_at,'') AS registered_at,

internal/commons/scoreboard_dump_test.go

@@ -30,6 +30,10 @@ func TestQueryScoreboardDump_Basic(t *testing.T) {
 	if dump.Rigs[0].DisplayName != "Alice Chen" {
 		t.Errorf("rig display_name = %q, want Alice Chen", dump.Rigs[0].DisplayName)
 	}
+	// alice has 1 root stamp (weight=5) → newcomer tier
+	if dump.Rigs[0].TrustTier != "newcomer" {
+		t.Errorf("rig trust_tier = %q, want newcomer", dump.Rigs[0].TrustTier)
+	}
 
 	if len(dump.Stamps) != 1 {
 		t.Fatalf("stamps count = %d, want 1", len(dump.Stamps))