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

Commit A fixes a real correctness bug: the previous code silently mapped a missing post lookup to index 0 (which is also a valid index for the first post), making the UI guard `if index > 0` meaningless and the link route (0-based) inconsistent with the displayed 1-based index; A aligns the indexing with the actual /t/tag/N route, replaces the silent fallback with an explicit invariant check, and adds tests asserting correct indices. Commit B is a reasonable UI refactor (grouping CLI hints, hover-to-copy, JS-safety assert) but is mostly cosmetic/feature polish without fixing an underlying correctness issue.