feat(plex): the person page in two columns; a bio on its way holds its place (E30 S6)

The biography sat at reading width in the left half of a full-width panel with nothing on the right.
Now the person (headshot, facts, the bio clamped to eight lines with More / Less when it is cut) is on the
left and "Known for" on the right; with fewer than four titles the rail takes only its posters' width.
One column where the panel is narrow (200% zoom, the largest text size).

While the server fetches a bio (`enriching`), the page shows a paragraph skeleton (a new "text" shape of
LoadingState) and asks again every 1.5 s for up to 20 s. The view is keyed by the person's name, so
another person starts fresh.

frontend/src/components/PlexBrowse.tsx

@@ -468,7 +468,9 @@ export default function PlexBrowse() {
   if (sub.view.kind === "person") {
     const personName = sub.view.name;
     return (
+      // Keyed by the name: another person is a fresh page (their own bio wait, a collapsed bio).
       <PlexPersonView
+        key={personName}
         name={personName}
         onBack={sub.back}
         onOpenCard={onCard}