~x-ai/grok-latest → A (8:1)

Commit A makes a real semantic fix: switches rank-history thread_post_index to consistent 0-based indexing matching /t/tag/N routes, replaces silent unwrap_or(0) with expect, drops the conditional UI hide, documents the contract, and adds integration assertions. Commit B is almost entirely rustfmt churn across examples and crates plus minor tooling (toolchain components, VS Code settings, one duplicated CSS rule merge), which adds little lasting design or correctness value.