MAC6: a snapshot mutation carries its video count back to the list cache.
MAC8: playlist rows and cards are Buttons with the context menu attached,
so macOS accessibility can reach Edit and Delete.
MAC10: a published date stamped with the request's own time is dropped at
both API sentinels, and formattedPublishedDate refuses zero-interval output.
MAC11: a failed history hydration shows Details unavailable with a Try
Again action instead of keeping the raw video ID forever; an empty 200
body is a legible failure.
