The library is the accounts' shelf, but the tab kept two copies of that fact: the
screen read `/me` once as it mounted and then stopped listening, so a visitor who
signed in at the studio came back to the panel asking for the login they had just
given. One record, read by the studio, the landing page and the shelf alike, is
now the only copy — a sign-in anywhere is a sign-in everywhere.
- auth.ts (new): the tab's one session record. `useAuth()` reads it through
`useSyncExternalStore`, a `/me` already in flight is joined rather than
repeated, and a call that fails leaves the record *unknown* rather than signed
out, so a cold API never reads as a guest.
- TopBar: LIBRARY is a link for a member and a dead button for everyone else. An
anchor wearing `aria-disabled` still navigates on a click, and the screen
behind it would only send the guest home again — so a guest gets the shape of
the button and nothing to press.
- Library: the gate is that shared record, not a copy taken at mount. A guest who
opens `/library` straight is turned home with `replace`, so a Back press does
not walk them into the same wall. The screen is mounted the whole time the tab
is open, so the turn is for the address the visitor actually opened: a guest on
the studio stays on the studio.
- engine/library.ts: the thumbs hand the thread back. Two lanes instead of four,
a frame's worth of idle between them, and one job per frame — a second caller
joins the decode already running instead of starting another.
Verified in Chrome (stubbed API, harness run against both the dev server and the
built bundle): a guest gets a dead LIBRARY button and stays on /app; signing in at
the studio turns it into the link and opens the shelf, with no second login and no
"log in to browse" note; the same after a sign-in on the landing page; /library
opened cold as a guest lands on / with Back going to /app; opened cold signed in,
the shelf is up. On a folder of 22 frames the open runs 2 decodes at a time (was
5) and repeats no frame (44 decodes, was 56 — 12 frames were read twice); the
tiles still come out 22 on the open, 24 by hand, 22 again after a reload.
3dtours
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