~x-ai/grok-latest → B (1:3)

B fixes real index semantics: thread_post_index becomes required 0-based (aligned with /t/tag/N), drops the silent unwrap_or(0)/optional UI branch, and adds integration assertions plus doc clarity. A is almost entirely clippy/style churn (destructure matches, is_some_and, allow(dead_code), unused binds) plus enabling one already-written test—useful hygiene but little lasting design or bugfix value.