refactor(web): shrink LayoutShell.documentsPanel interface (fixes #1360)

The `documentsPanel` prop on `LayoutShell` declared `isDocked` and
`onDockedChange` alongside `open` / `onOpenChange`, but the shell never
forwarded those two extra fields to its consumers. `RightPanel` already
defines its own interface accepting only `open` / `onOpenChange`, and
`DocumentsSidebar` keeps both as optional props with safe fallbacks for
the rare cases that pass them directly.

Trim the interface to the two fields the shell actually plumbs through
and drop the matching `isDocumentsDocked` state and prop entries from
`LayoutDataProvider`, which was the only caller still populating the
dead fields (`FreeLayoutDataProvider` already passed the minimal pair).
`DocumentsSidebar` itself is untouched — its props remain optional so
direct consumers that want docking behaviour can still wire it.

surfsense_web/components/layout/ui/shell/LayoutShell.tsx

@@ -157,8 +157,6 @@ interface LayoutShellProps {
 	documentsPanel?: {
 		open: boolean;
 		onOpenChange: (open: boolean) => void;
-		isDocked?: boolean;
-		onDockedChange?: (docked: boolean) => void;
 	};
 	onTabSwitch?: (tab: Tab) => void;
 }