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

Commit B introduces a substantive new abstraction (RouteContext wrapping ThreadNav with concrete methods) plus a detailed migration plan document that provides real architectural direction and lasting reference value for future refactors. Commit A is a trivial one-line-block removal of dead HTML markup, which is useful cleanup but minor in scope and impact compared to B's added scaffolding and documentation.