Previously loadMessagesFromDB swallowed all errors and returned [] — a
network failure was indistinguishable from an empty history, so the user
had no way to know loading failed. Now the function returns
{ messages, error } and the MyChatPanel renders a role="alert" banner
with the error message and a Retry button when messages are empty and
a load error occurred.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>