Android half of ios#33. Same shape as iOS: the muted set lives in the
vault beside the audience list, because who somebody has muted is a
statement about their social graph and shared preferences are readable
by anything that reaches the file.
The filter runs on the way out of `stories()`, after `saveStories` has
already written the live set back. A muted contact's stories are still
received and still stored — dropping them on receipt would be cheaper,
but unmuting would then show an empty strip until their next post, and
muting would quietly mean something other than what it says.
`Vault.visibleStories` never drops the signed-in user, even if their own
id is in the set. `setStoryMuted` refuses to put it there, but a restored
backup from a build without that guard could carry one, and hiding
somebody's own posts from them reads as the posts having failed to send.
Long press on a story bubble to hide or restore.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
