Pieces: the Gallery, as a section like Collections

The Gallery is a flat list of peças, each with a title, a gallery of mixed
media, and the specs from the client's sitemap — measurement, raw material,
colours, and NOTAS: production time and shipping conditions.

That is a collection one level flatter, so the panel is shared rather than
copied. SubjectPanel and SubjectFields take a section config (subjects.ts);
CollectionsPanel and PiecesPanel are one line each.

The five template blocks are renamed collection-* to subject-*. They never read
anything collection-specific, and copying them per section would have meant
twenty kinds by the time Drops and Collabs land.

Called Pieces in the nav, not Gallery — there is already a Galleries section
meaning a named set of media, and two rows called Gallery and Galleries is a
question somebody has to answer every time they look at it.

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

web/sections/PageBuilderPanel.tsx

@@ -23,11 +23,12 @@ const LABELS: Record<string, string> = {
   'contact-form': 'Contact form',
   partners: 'Partners',
   collections: 'Collections',
-  'collection-cover': 'Lead photograph',
-  'collection-title': 'Name',
-  'collection-description': 'Description',
-  'collection-specs': 'Specs',
-  'collection-gallery': 'Photographs',
+  pieces: 'Pieces',
+  'subject-cover': 'Lead photograph',
+  'subject-title': 'Name',
+  'subject-description': 'Description',
+  'subject-specs': 'Specs',
+  'subject-gallery': 'Photographs',
 };
 
 /*
@@ -40,12 +41,13 @@ const PLACES_ONLY: string[] = [
   'contact-form',
   'partners',
   'collections',
-  // The subject blocks hold nothing either: what they draw is the collection the URL names.
-  'collection-cover',
-  'collection-title',
-  'collection-description',
-  'collection-specs',
-  'collection-gallery',
+  'pieces',
+  // The subject blocks hold nothing either: what they draw is the row the URL names.
+  'subject-cover',
+  'subject-title',
+  'subject-description',
+  'subject-specs',
+  'subject-gallery',
 ];
 import { AddSectionDialog, type SectionLayout } from './AddSectionDialog';
 import { FreeTextEditor } from './FreeTextEditor';