openai/gpt-chat-latest → B (5:1)

Side B makes a functional architectural change by replacing the durable recent-vote deque with an append-only list, removing post-write trimming, updating the in-memory representation to `Vec`, bumping the storage schema version, and adding a test that verifies query-time capping of recent votes. Side A mostly adds a detailed planning document plus a thin `RouteContext` wrapper re-export around `ThreadNav`, which introduces little immediate behavior beyond an API convenience layer.