community refactor left broken examples and edge-case regressions

[tomcasaburi]

Several follow-up issues remain after the subplebbit to community refactor, including broken docs examples, account-scoping leaks in useAccountCommunities, incomplete error reporting in useCommunityStats, and a few mock/store edge cases. These inconsistencies make the renamed API harder to trust and can cause incorrect runtime behavior in non-happy paths.