Collabs, as a third configuration of one panel

The same object as a collection and a gallery piece, so it is a config in
subjects.ts and a one-line panel — no new screen.

Two differences, both deliberate. It has no SPECS: a collab is a project rather
than an object, so there is no measurement or raw material and the form is a
name, an address and a description. And its title column is `project_name`,
which is the client's word and stays — the site's API publishes both that and
`title` so this panel reads one field like every other section, and the
translation lives in one router rather than as a branch in every screen.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

web/DetailPanel.tsx

@@ -6,6 +6,7 @@ import { sectionFor, sectionOpen, type SectionKey } from './sections';
 import { AdministrationPanel } from './AdministrationPanel';
 import { MediaPanel } from './MediaPanel';
 import { CollectionsPanel } from './sections/CollectionsPanel';
+import { CollabsPanel } from './sections/CollabsPanel';
 import { PiecesPanel } from './sections/PiecesPanel';
 import { CarouselsPanel } from './sections/CarouselsPanel';
 import { LayoutPanel } from './sections/LayoutPanel';
@@ -50,6 +51,7 @@ const PANELS: Partial<Record<SectionKey, () => React.JSX.Element>> = {
   layout: LayoutPanel,
   collections: CollectionsPanel,
   pieces: PiecesPanel,
+  collabs: CollabsPanel,
   carousels: CarouselsPanel,
   messages: MessagesPanel,
   administration: AdministrationPanel,