feat(accounts): name the instance an account belongs to

[kipavy]

Every switch-target row read "Cloud", so an account on the official cloud and one on a self-hosted instance were indistinguishable — same email, same icon, same sublabel. SavedAccount already carried server_url; only the design was missing.

The rule

Mark only what is not the default, in slots that already exist. No new row, no new line, no extra width. An official-cloud account is byte-for-byte unchanged.

Surface	Official cloud	Self-hosted
Switch row	circle-user + "Cloud"	lucide:server + stackdome.example.tld, full URL in the hover title
Account header	circle-user + "Cloud account"	lucide:server + the host
Auth server field	collapsed, "Custom server URL"	open, "Server: <host>"

Considered and rejected: the hostname on every row (pushes a URL at people who only ever use one instance), an icon swap with no text (two self-hosted instances stay ambiguous), and user-assigned nicknames (a whole editing surface; deliberately deferred).

How the label is derived

src/utils/serverInstance.ts — hostname, a leading api./www. dropped only when the rest still contains a dot, a non-default port kept because it is what distinguishes two instances on one host. Anything absent or unparseable counts as the default: better unmarked than mislabelled.

server_url	Label
https://api.voltius.app	"Cloud" — never marked
https://stackdome.example.tld	stackdome.example.tld
https://api.stackdome.example.tld	stackdome.example.tld
http://192.168.1.40:8443	192.168.1.40:8443
https://api.local	api.local — stripping would leave a bare name
null / unparseable	"Cloud"

The auth screen, and why it needed a device-scoped record

"Add another account…" landed on the auth screen with the server field collapsed and reset to https://api.voltius.app, so aiming at a self-hosted instance was one un-clicked disclosure away from silently registering on the official cloud.

Auto-expanding on a non-default value is not reachable on its own: adding an account clears server_url along with every other ACCOUNT_CACHE_KEYS entry, so the screen has nothing non-default to open on. The field now seeds from voltius.last-server-url — device-scoped localStorage, written on a successful sign-in, surviving teardown because clearPersistedAccountUiState removes only its explicit key list.

Duplications collapsed on the way

• DEFAULT_SERVER lived in both AuthPage.tsx and CloudAuthModal.tsx, as did the disclosure block. Both now use ServerUrlField; the screens disagreed only about input styling, which is one inputClassName prop.
• Four routes into a server session — register, login re-auth, signInToCloud, linkToCloud — each wrote the same keychain list by hand. persistServerSession is now the single place that writes it, and the single place that records the instance, which a fifth route would otherwise forget.

Testing

Suite 3758/3758 across 483 files; tsc --noEmit exit 0. New: 14 tests for the label rules and the remembered instance, 3 for ServerUrlField, 4 in SidebarAccountButton.switcher.test.tsx (two accounts sharing an email on different instances, the server icon and title, and both header cases), 2 in account.serverAuth.test.ts (a successful registration remembers the instance, a failed one leaves it alone).

⚠️ Not live-clicked. Unit tests only — proving the two-instance case end to end needs a real self-hosted server.