chore(readme): mirror profile layout in preview, demo uses Monday start

- Project README preview section collapses the two side-by-side tables into
  one centred table matching tiennm99/tiennm99's stats table (row order
  identical to the per-theme demo pages).
- demo.yml now renders with -start-of-week monday so the gallery showcases
  the new flag and stays visually consistent with the author profile.

.github/workflows/demo.yml

@@ -40,6 +40,7 @@ jobs:
             -user "${{ github.repository_owner }}" \
             -themes all \
             -tz Asia/Saigon \
+            -start-of-week monday \
             -out demo
 
       - name: Write demo READMEs (index + per-theme)