feat(design): titles in click surfaces stay selectable (E28 S3e4b)

A button whose text is a title or a name is now `selectable` (FocusSafeButton,
under Pressable and Button): Chrome selects inside a button once it is
user-select: text (measured), and the click that ends a selection, or a press
dragged past the slop, opens nothing. 23 surfaces carry it (cards, rows, people,
channels, playlists, users, views, messages, log lines, description links); the
Plex caption div gets the same guard. A contract test pins every plain Pressable
with its reason, so a new one has to choose.

frontend/src/components/ChannelLink.tsx

@@ -30,6 +30,7 @@ export default function ChannelLink({
       <Avatar src={thumbnailUrl} fallback={title ?? ""} className="w-8 h-8 rounded-full shrink-0" />
       {onView ? (
         <Pressable
+          selectable
           onClick={onView}
           // The channel's "open" element: in a keyboard-walkable list (lib/listNav) Enter on the row or
           // card clicks this.