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>

docs/project/backlog/WP-24-letter-canvas.md

@@ -94,6 +94,6 @@ polish + standaardbrief + diff badges (WP-27).
 ## Risks
 
 The canvas duplicates the letter markup that WP-25's backend renderer will emit —
-acceptable *only* because `letter.css` is shared and WP-25 adds the class-parity
+acceptable _only_ because `letter.css` is shared and WP-25 adds the class-parity
 test; until WP-25 lands, the canvas is the sole consumer, so no drift is possible.
 Deleting `letter-preview` breaks any deep import of it — repo-wide grep before delete.