Startup no longer looks for an AlchementaryLink data directory to copy
into NexusTerminal, and the 'Imported your Alchementary Link data' toast
and the migration docs are gone. Existing Alchementary Link installs are
no longer picked up automatically.
- Secrets::delete_profile removes every profile credential kind from the OS
keychain as well as the vault (previously only the vault was purged, so
keychain passwords/tokens outlived the profile).
- write_private writes to a sibling temp file and renames it into place, so a
crash mid-write cannot truncate the vault or an export, and a pre-existing
world-readable file is replaced rather than reused.
- Argon2-derived vault/export keys are Zeroizing and wiped on drop.
- Recordings (which capture typed input), JSON exports and --data-dir
directories are created owner-only.
Andy Dixon