Shell: grouped, collapsible, multi-column per-tile settings popover

The gear popover learns the admin form's conventions: an instanceSchema
field's `group` starts a labeled subsection, `help` puts a line of guidance
under a control, and a manifest `instanceGroups[name]` adds
{ collapsed, columns, help } for that group (rendered as <details> with a
grid body; container queries drop to two or one column in narrow tiles).
/api/modules now exposes instanceGroups. Lets a module keep a long
show/hide checklist per tile — where display choices belong — without
the popover turning into a scroll of thirty loose checkboxes.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

server.js

@@ -402,6 +402,7 @@ async function clientManifest(id) {
     minSize: man.minSize || { w: 1, h: 1 },
     defaultSize: man.defaultSize || { w: 4, h: 3 },
     instanceSchema: man.instanceSchema || {},
+    instanceGroups: man.instanceGroups && typeof man.instanceGroups === 'object' ? man.instanceGroups : {},
     hasServer: Boolean(man.server),
     config: clientConfig(id),
     tiles: await moduleTiles(id),