fix: prevent skill name wrapping in mini cards with single-line ellipsis

The skill name heading was wrapping to multiple lines for long names like
'Two-digit with ones place regrouping', causing the card height to change
and buttons to shift position.

**Fix:**
- Added whiteSpace: 'nowrap' to force single line
- Added overflow: 'hidden' and textOverflow: 'ellipsis' to truncate
- Added flex: 1 to allow name to take available space

Now the skill name always stays on exactly one line with ellipsis (...)
if it's too long, keeping the card height perfectly consistent.

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

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

apps/web/src/app/create/worksheets/addition/components/config-panel/MasteryModePanel.tsx

@@ -320,6 +320,10 @@ export function MasteryModePanel({ formState, onChange, isDark = false }: Master
                     fontWeight: '600',
                     color: isDark ? 'white' : 'gray.900',
                     lineHeight: '1.2',
+                    overflow: 'hidden',
+                    textOverflow: 'ellipsis',
+                    whiteSpace: 'nowrap',
+                    flex: 1,
                   })}
                 >
                   {currentAdditionSkill.name}
@@ -479,6 +483,10 @@ export function MasteryModePanel({ formState, onChange, isDark = false }: Master
                     fontWeight: '600',
                     color: isDark ? 'white' : 'gray.900',
                     lineHeight: '1.2',
+                    overflow: 'hidden',
+                    textOverflow: 'ellipsis',
+                    whiteSpace: 'nowrap',
+                    flex: 1,
                   })}
                 >
                   {currentSubtractionSkill.name}