feat: close the shift with a Thoreau quote in the end letterbox

src/content/schemas.ts

@@ -231,6 +231,7 @@ const portfolioContentSchema = z.object({
     afterglow: soundtrackAssetSourcesSchema,
     driveLift: soundtrackAssetSourcesSchema,
   }).strict().optional(),
+  closer: z.object({ quote: visibleString, attribution: visibleString }).strict().optional(),
   sceneDescription: visibleString,
 }).strict().superRefine((content, context) => {
   const navigationIds = content.navigation.map((item) => item.id);

src/content/types.ts

@@ -175,6 +175,8 @@ export interface PortfolioContent {
   contact: ContactContent;
   metadata: MetadataContent;
   soundtrack?: SoundtrackContent;
+  /** Public-domain closing quote shown in the end-of-shift letterbox. */
+  closer?: { quote: string; attribution: string };
   sceneDescription: string;
 }