feat: responsive grid with scrollable area and fixed hint column

- Add CSS variables (--cell, --cell-font, --trigger-h) for responsive cell sizing
- Shrink grid cells at 600px and 420px breakpoints
- Add .page-body wrapper with 16px horizontal padding to prevent edge collisions
- Separate hint column from scrollable grid: hints rendered outside the table in a fixed flex column, only the letter grid scrolls horizontally

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

assets/react/controllers/GameRow.jsx

@@ -1,12 +1,11 @@
 import React, { useRef, useCallback, useMemo } from 'react';
 import LetterInput from './LetterInput';
-import ActorPopover from './ActorPopover';
 
 function isLetter(ch) {
     return /[a-zA-Z]/.test(ch);
 }
 
-export default function GameRow({ actorName, pos, colStart, totalWidth, hintType, hintText }) {
+export default function GameRow({ actorName, pos, colStart, totalWidth }) {
     const inputRefs = useRef([]);
     const letters = actorName.split('');
 
@@ -29,9 +28,6 @@ export default function GameRow({ actorName, pos, colStart, totalWidth, hintType
 
     return (
         <tr>
-            <td>
-                <ActorPopover hintType={hintType} hintText={hintText} />
-            </td>
             {Array.from({ length: totalWidth + 1 }, (_, colIndex) => {
                 const charIndex = colIndex - colStart;
                 const isInRange = charIndex >= 0 && charIndex < letters.length;