This commit modifies `js/userBlocks.js` to correctly parse Kind 10000 events that have empty content but populated `p` tags (used by clients like Primal). Previously, these events were treated as empty block lists, causing the user's block list to be cleared.
Changes:
- Refactored `loadBlocks` to check for empty content and fallback to extracting pubkeys from tags using `extractPubkeysFromTags`.
- Updated `loadBlocks` to use a sequential promise strategy (`Promise.any` then `Promise.allSettled`) to ensure eventual consistency without race conditions or double-processing.
- Added extensive tests in `tests/user-blocks.test.mjs` covering tag-only lists, whitespace content, and concurrency scenarios.