fix: replace invalid CSS 'space' property with 'gap' in guide page

Updated Panda CSS styling to use the correct 'gap' property instead of the
invalid 'space' property that was causing TypeScript compilation errors.
This ensures proper spacing in ordered lists.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

apps/web/src/app/guide/page.tsx

@@ -767,7 +767,7 @@ function ArithmeticOperationsGuide() {
           </h4>
           <ol className={css({
             pl: '6',
-            space: 'y-2',
+            gap: '2',
             color: 'gray.700'
           })}>
             <li className={css({ mb: '2' })}>1. Set the first number on the soroban</li>
@@ -843,7 +843,7 @@ function ArithmeticOperationsGuide() {
           </h4>
           <ol className={css({
             pl: '6',
-            space: 'y-2',
+            gap: '2',
             color: 'gray.700'
           })}>
             <li className={css({ mb: '2' })}>1. Set the minuend (first number) on the soroban</li>