providers is a panel, not a section in officer's settings

`IntegrationsSettings/index.tsx` has carried the rule since email was extracted
on 2026-08-18: a plugin contributes panels, not settings sections. the
extraction brief said the opposite and the brief was wrong.

settings living in the platform mean this plugin is not self-contained — it
cannot be configured on an older platform, and uninstalling would leave a dead
"Atelier" section in the settings screen for someone to delete by hand.

so: a fourth panel, `atelier-providers`, and the default layout stacks it under
Collections in the right column. smallest and last because it is configured once
and then ignored — but it has to be REACHABLE, which is the whole point.

Generate's empty state pointed at "Settings → Integrations → Atelier". it now
points at the Providers panel, which is where the key actually goes.

web/layout.ts

@@ -1,8 +1,15 @@
 import type { LayoutNode } from 'officerdev';
 
 // Generate stays narrow and fixed — it is a form, not a working area. Gallery gets the most room: it
-// is the main "what did I make" view. Collections is the organising view, smallest of the three. Users
-// can resize or rearrange freely; this is only the starting point.
+// is the main "what did I make" view. The right column stacks the two organising views: Collections
+// above, Providers below.
+//
+// Providers is here rather than in Officer's settings because a plugin contributes panels, not settings
+// sections — the rule `IntegrationsSettings/index.tsx` states for email. It is placed smallest and last
+// because it is configured once and then ignored, but it has to be REACHABLE, and a plugin whose only
+// configuration screen lives in the platform is not self-contained.
+//
+// Users can resize or rearrange freely; this is only the starting point.
 export const defaultLayout: LayoutNode = {
   type: 'group',
   id: 'atelier-root',
@@ -10,6 +17,17 @@ export const defaultLayout: LayoutNode = {
   children: [
     { node: { type: 'panel', id: 'atelier-generate', appType: 'atelier-generate' }, size: 26 },
     { node: { type: 'panel', id: 'atelier-gallery', appType: 'atelier-gallery' }, size: 48 },
-    { node: { type: 'panel', id: 'atelier-collections', appType: 'atelier-collections' }, size: 26 },
+    {
+      node: {
+        type: 'group',
+        id: 'atelier-side',
+        direction: 'vertical',
+        children: [
+          { node: { type: 'panel', id: 'atelier-collections', appType: 'atelier-collections' }, size: 60 },
+          { node: { type: 'panel', id: 'atelier-providers', appType: 'atelier-providers' }, size: 40 },
+        ],
+      },
+      size: 26,
+    },
   ],
 };