fix: resolve golangci-lint errors (errcheck, staticcheck)

- Wrap defer rows.Close() to check error in postgres.go and sqlite.go
- Discard unused return value in a2a_bridge.go

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: gcmsg

internal/registry/postgres.go

@@ -350,7 +350,7 @@ func (s *PostgresStore) GetAccessFlagsBatch(ctx context.Context, ids []string) (
 	if err != nil {
 		return nil, fmt.Errorf("get access flags batch: %w", err)
 	}
-	defer rows.Close()
+	defer func() { _ = rows.Close() }()
 
 	result := make(map[string]*AccessFlags, len(ids))
 	for rows.Next() {

internal/registry/sqlite.go

@@ -368,7 +368,7 @@ func (s *SQLiteStore) GetAccessFlagsBatch(ctx context.Context, ids []string) (ma
 	if err != nil {
 		return nil, fmt.Errorf("get access flags batch: %w", err)
 	}
-	defer rows.Close()
+	defer func() { _ = rows.Close() }()
 
 	result := make(map[string]*AccessFlags, len(ids))
 	for rows.Next() {

internal/server/a2a_bridge.go

@@ -182,7 +182,7 @@ func (s *HTTPServer) handleA2ABridgeSendMessage(w http.ResponseWriter, r *http.R
 
 	// Synchronous: collect all chunks from stream.
 	if s.bridges == nil {
-		task = s.updateTaskState(task, a2a.TaskStateFailed, "bridge not available")
+		_ = s.updateTaskState(task, a2a.TaskStateFailed, "bridge not available")
 		writeA2ABridgeError(w, req.ID, jsonrpc.CodeInternalError, "bridge not available")
 		return
 	}