"Acting as" read like a choice of Sia account; it picks an S3 user on
this s3d, and every user shares the one Sia account the s3d is connected
to. So:
- The picker is "S3 user", with a tooltip saying all users share one Sia
account; Buckets explains what a bucket is.
- Buckets and the Overview show "Sia account: <label> (indexer)". Pithos
cannot see the account's email, so the Sia connection page lets the
user label it (kept in pithos.json beside the s3d data).
- "Switch Sia account" stops s3d and moves its data (connection, users,
keys, buckets, upload buffer) into previous-account-<stamp>/ next to
s3d.yml, never deleting it; the guide then connects another account.
It warns about uploads still waiting for Sia and offers a flush, and
refuses while another s3d serves the config.
- "Earlier Sia accounts" lists those folders with Restore, which sets the
current account aside the same way and swaps the old one back.
Also: a fresh connect now records which indexer it used, and a "not
connected" check is re-run after 30 s so a login made outside Pithos
shows up.
