Administration sits at the foot of the panel, not the end of the list

it was last in SECTIONS, so it rendered as the tenth row and then stopped —
directly under Messages, with empty panel beneath it. that is the bottom of the
LIST. what it wanted is the bottom of the PANEL, the way Update-all sits in the
plugins nav.

`mt-auto` on a second group, divided by the same border the rows already use. it
holds whether there are ten sections or two, and it does not need a spacer element
to push it down.

the split is a `pinned` flag on the section rather than the nav testing for the
key. which sections are the client's site and which are this plugin's own
machinery is a fact about the section, and the nav should be reading it, not
knowing it. one array still — `sectionFor` and `isSectionKey` have to resolve
every key, and a second exported list is a second place to forget one.

the row body came out into `renderRow` so both groups draw the same row. no
change to what a row looks like.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/sections.ts

@@ -48,6 +48,15 @@ export type Section = {
   /** The fofos path this reads, relative to the plugin's mount. Null when nothing is built. */
   path: string | null;
   built: boolean;
+  /**
+   * Pinned to the FOOT of the nav rather than sitting in the list.
+   *
+   * A flag rather than the nav hard-coding a key, because "which sections are the site's and which are
+   * the plugin's own" is a fact about the section. It is also why this stays in one array: `sectionFor`
+   * and `isSectionKey` have to resolve every key, and a second exported list would be a second place to
+   * forget one.
+   */
+  pinned?: boolean;
 };
 
 export const SECTIONS: Section[] = [
@@ -135,6 +144,7 @@ export const SECTIONS: Section[] = [
     hint: 'Where fofos is, and the token to reach it',
     path: null,
     built: true,
+    pinned: true,
   },
 ];