~anthropic/claude-sonnet-latest → B (6:4)

Both patches implement the same core fix (drop shared sentinel delegates so multi-user votes work) with identical new tests, but B goes further and cleans up all the now-dead sentinel machinery: it removes the unused `is_browser_sentinel_delegate` helper and its `mod.rs` re-export, simplifies `authorship_attr`/`authorship_color_seed` in `html/mod.rs` to drop sentinel-checking branches, and deletes the now-obsolete `browser_sentinel_delegate_shows_username` test. A leaves this related dead code and tests untouched, so B's diff represents a more complete and consistent refactor with less leftover cruft.