style: format the repo with prettier (green format:check)

`npm run format:check` (a CI gate) had drifted red across 44 files — pre-existing
files plus recently-added ones committed without formatting. Ran `prettier --write .`;
no logic changes. Also regenerates documentation.json (compodoc reflects the reformatted
component sources).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/brief/domain/brief-diff.spec.ts

@@ -3,7 +3,11 @@ import { Brief, LetterBlock } from './brief';
 import { diffBlocks, changedBlocks } from './brief-diff';
 
 function block(id: string, text: string): LetterBlock {
-  return { type: 'freeText', blockId: id, content: { paragraphs: [{ nodes: [{ type: 'text', text }] }] } };
+  return {
+    type: 'freeText',
+    blockId: id,
+    content: { paragraphs: [{ nodes: [{ type: 'text', text }] }] },
+  };
 }
 
 function brief(blocks: LetterBlock[]): Brief {