style: format codebase per updated .prettierrc (2 → 4 space indent)

The quality-refactor commit changed .prettierrc tabWidth from 2 to 4
but left the rest of the repository on the old indentation, breaking
the pre-push prettier --check guard. This is a mechanical reformat of
all 108 affected files via `npx prettier --write .`. Pure whitespace,
no semantic changes. Test suite remains 1097/1097 passing.