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>

docs/MODULE-GUIDE.md

@@ -106,6 +106,12 @@ the group name:
 placeholders, where a value comes from. Keep labels short and put the
 explanation there.
 
+`group` and `help` work on `instanceSchema` fields too, and a manifest
+`instanceGroups` map plays the `configGroups` role for the tile's gear
+popover (`collapsed: true | false`, `columns`, `help`). That is how a module
+with a long show/hide checklist keeps the popover usable — see `pco-plan`.
+Display choices belong there, per tile; admin config is for connections.
+
 `showWhen: "<key>"` hides a field until the boolean/`switch` field named
 `<key>` is on — e.g. the audio device and channel appear only once the LTC
 listener switch is enabled. The hidden field still keeps its stored value.