fix: dice view readability and pool builder cleanup

Remove d100 from the dice pool builder (percentile section is
unaffected). Switch die buttons, pool display, and result output
to JetBrains Mono for mechanical/numeric readability, and lay out
the pool builder buttons in a fixed 7-column grid to match the
remaining die count.

public/index.html

@@ -233,7 +233,6 @@
             <button class="die-btn" data-sides="10">d10</button>
             <button class="die-btn" data-sides="12">d12</button>
             <button class="die-btn" data-sides="20">d20</button>
-            <button class="die-btn" data-sides="100">d100</button>
             <button class="die-btn" data-sides="2">d2</button>
           </div>