ci: auto-fix prettier formatting in pre-commit hook and CI (#498)

Pre-commit hook:
- Stage all files modified by prettier:fix, not just src/generated/

CI (GitHub Actions):
- Add prettier-fix job that runs on PRs from the same repo
- Auto-commits formatting fixes back to the PR branch
- Skips fork PRs (no write access to fork branches)

Co-authored-by: Claude <noreply@anthropic.com>

.husky/pre-commit

@@ -17,5 +17,5 @@ fi
 npm run build:all
 npm run prettier:fix
 
-# Stage any changes to generated files (they may have been reformatted by prettier)
-git add src/generated/
+# Stage any files reformatted by prettier (generated files, source, docs, etc.)
+git diff --name-only --diff-filter=M | xargs -r git add