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

Side A fixes a real concurrency bug (shared sentinel delegate blocking multi-user votes) with a minimal, well-targeted change plus a direct regression test proving the fix. Side B is a large URL-encoding refactor (dropping the '/' between room short-id and slug) that changes external URL identity/canonicalization behavior broadly, touches many call sites and tests, and bundles in unrelated YouTube URL normalization logic, increasing risk and surface area without a clearly motivated bug being fixed.