fix: restrict inbox to captured artifacts

internal/core/nodes/repository.go

@@ -169,10 +169,13 @@ func (r *Repository) ListRoots(includeDeleted bool) ([]Node, error) {
 	return scanNodes(rows)
 }
 
-// ListInboxRoots returns active root nodes that are not assigned to a specific section.
+// ListInboxRoots returns active root capture artifacts explicitly marked for inbox.
 func (r *Repository) ListInboxRoots(includeDeleted bool) ([]Node, error) {
 	q := `SELECT ` + nodeColumns + ` FROM nodes
-		WHERE parent_id IS NULL AND COALESCE(section, '') IN ('', 'inbox')`
+		WHERE parent_id IS NULL
+		AND id IN (
+			SELECT node_id FROM node_meta WHERE key = 'capture.inbox' AND value = 'true'
+		)`
 	if !includeDeleted {
 		q += " AND deleted_at IS NULL"
 	}