web: three panels — Generate, Gallery, Collections — and a layout

ported from the standalone app's hash-tab UI. The panels do not coordinate through props (the panel
contract only ever hands a component its panelId) or usePanelChannel-as-selection:

- Gallery's lightbox is ?selected=<id>, Collections' detail is ?collection=<id> — different names
  since both panels render on the same route at once
- Generate bumps useAtelierRefresh (added to officerdev/src/channels.ts) when a job finishes;
  Gallery subscribes to it — a genuine signal, not a selection, so it stays a channel

images render through GET /files/:filename with a ?token= query param appended client-side
(lib/api.ts's fileUrl), the same escape hatch FileViewer and the music plugin use for exactly this:
a browser cannot set an Authorization header on an <img src>.

Providers is not here — see PLUGIN.md for why it became a platform settings screen instead.

assets/icon.png and assets/splash.png are [placeholder] flat swatches, not real artwork — see
assets/PLACEHOLDER.md.

web/panels.ts

@@ -0,0 +1,19 @@
+import type { AppRegistryMeta } from 'officerdev';
+import { Sparkles, GalleryHorizontalEnd, FolderOpen } from 'lucide-react';
+import { Generate } from './Generate/Generate';
+import { Gallery } from './Gallery/Gallery';
+import { Collections } from './Collections/Collections';
+
+// No component re-exports. `panels.ts` declares PANELS — the shell mounts them by key and there is no
+// way to export a component from a plugin.
+//
+// The three coordinate through the URL and one refresh channel, never through props: Gallery reads
+// `?selected=<id>` for its lightbox, Collections reads `?collection=<id>` for its detail view — two
+// different param names on purpose, since both panels render on the same route at once and would
+// otherwise fight over one param. Generate bumps `useAtelierRefresh` (officerdev/src/channels.ts) when
+// a job finishes; Gallery subscribes to it. See plugins/atelier/PLUGIN.md.
+export const appRegistryMetas: AppRegistryMeta[] = [
+  { key: 'atelier-generate', name: 'Generate', icon: Sparkles, component: Generate, availableOnPanel: false },
+  { key: 'atelier-gallery', name: 'Gallery', icon: GalleryHorizontalEnd, component: Gallery, availableOnPanel: false },
+  { key: 'atelier-collections', name: 'Collections', icon: FolderOpen, component: Collections, availableOnPanel: false },
+];