Media payload writes used .atomic alone and inherited the container
default; the courier store, outbox, gossip archive, and receipt index
all state their protection class at the write site. Media now follows
the same convention: until-first-user-authentication on payload writes
and on every site that creates a media directory (the store's helpers,
live captures, the outgoing writers, and the files/ root creators), so
recordings that save as they go inherit it. A best-effort launch
migration stamps files written by older builds, applying only to items
at the container default or weaker so it can never downgrade, running
detached after the retention sweep from #1484. On stock devices the
container default already yields this class, so behavior does not
change; the protection is now stated in the code instead of inherited.
Full iOS suite green; macOS builds; swiftlint adds no violations.
Co-authored-by: jack <212554440+jackjackbits@users.noreply.github.com>
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