Apply suggestions from code review

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: qmuntal

go/client.go

@@ -904,7 +904,7 @@ func (c *Client) DeleteSession(ctx context.Context, sessionID string) error {
 // Example:
 //
 //	if client.State() == copilot.StateConnected {
-//	    session, err := client.CreateSession(nil)
+//	    session, err := client.CreateSession(context.Background(), nil)
 //	}
 func (c *Client) State() ConnectionState {
 	return c.state

go/session.go

@@ -209,7 +209,7 @@ func (s *Session) SendAndWait(ctx context.Context, options MessageOptions) (*Ses
 	case err := <-errCh:
 		return nil, err
 	case <-ctx.Done(): // TODO: remove once session.Send honors the context
-		return nil, fmt.Errorf("timeout after %v waiting for session.idle", ctx.Err())
+		return nil, fmt.Errorf("waiting for session.idle: %w", ctx.Err())
 	}
 }