fix(homepage): set fixed width for tutorial panel to prevent layout shift

Set the tutorial panel (left side) to a fixed width of 500px on desktop
to prevent the layout from shifting when switching between tutorials
with different text lengths.

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

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

apps/web/src/app/page.tsx

@@ -163,7 +163,13 @@ export default function HomePage() {
                   })}
                 >
                   {/* Tutorial on the left */}
-                  <div className={css({ flex: '1', minW: '0' })}>
+                  <div
+                    className={css({
+                      flex: '1',
+                      minW: { base: '100%', md: '500px' },
+                      maxW: { base: '100%', md: '500px' },
+                    })}
+                  >
                     <TutorialPlayer
                       key={selectedTutorial.id}
                       tutorial={selectedTutorial}