fix: add mode descriptions and remove double borders

Address two issues with the tab-style mode selector:

1. Add back helpful description text
   - Each mode now shows its description below the tabs
   - Description updates based on active tab
   - Preserves the helpful context from the old button layout

2. Remove double borders
   - Remove wrapper div that added extra background/padding
   - Let mode-specific controls use their own styling
   - Eliminates visual layering conflicts
   - Creates cleaner, more native tab-to-content flow

Mode descriptions:
- 🎯 Smart: "Research-backed progressive difficulty with adaptive scaffolding per problem"
- 🎛️ Manual: "Full control over display options with uniform scaffolding across all problems"
- 🎓 Mastery: "Skill-based progression with automatic review mixing for pedagogical practice"

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

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

apps/web/src/app/create/worksheets/addition/components/ConfigPanel.tsx

@@ -105,39 +105,28 @@ export function ConfigPanel({ formState, onChange, isDark = false }: ConfigPanel
         isDark={isDark}
       />
 
-      {/* Mode Selector Tabs */}
+      {/* Mode Selector Tabs with description */}
       <ModeSelector
         currentMode={formState.mode ?? 'smart'}
         onChange={handleModeChange}
         isDark={isDark}
       />
 
-      {/* Mode-specific controls as tab content */}
-      <div
-        data-element="mode-content"
-        className={stack({
-          gap: '3',
-          padding: '1.5rem',
-          backgroundColor: isDark ? 'gray.700' : 'gray.50',
-          borderRadius: '0 0 8px 8px',
-          marginTop: '-1.5rem', // Connect visually to tabs
-        })}
-      >
-        {/* Smart Mode Controls */}
-        {(!formState.mode || formState.mode === 'smart') && (
-          <SmartModeControls formState={formState} onChange={onChange} isDark={isDark} />
-        )}
+      {/* Mode-specific controls - no wrapper, let controls style themselves */}
+      {/* Smart Mode Controls */}
+      {(!formState.mode || formState.mode === 'smart') && (
+        <SmartModeControls formState={formState} onChange={onChange} isDark={isDark} />
+      )}
 
-        {/* Manual Mode Controls */}
-        {formState.mode === 'manual' && (
-          <ManualModeControls formState={formState} onChange={onChange} isDark={isDark} />
-        )}
+      {/* Manual Mode Controls */}
+      {formState.mode === 'manual' && (
+        <ManualModeControls formState={formState} onChange={onChange} isDark={isDark} />
+      )}
 
-        {/* Mastery Mode Controls */}
-        {formState.mode === 'mastery' && (
-          <MasteryModePanel formState={formState} onChange={onChange} isDark={isDark} />
-        )}
-      </div>
+      {/* Mastery Mode Controls */}
+      {formState.mode === 'mastery' && (
+        <MasteryModePanel formState={formState} onChange={onChange} isDark={isDark} />
+      )}
     </div>
   )
 }

apps/web/src/app/create/worksheets/addition/components/ModeSelector.tsx

@@ -18,93 +18,115 @@ export function ModeSelector({ currentMode, onChange, isDark = false }: ModeSele
       id: 'smart' as const,
       emoji: '🎯',
       label: 'Smart Difficulty',
+      description: 'Research-backed progressive difficulty with adaptive scaffolding per problem',
     },
     {
       id: 'manual' as const,
       emoji: '🎛️',
       label: 'Manual Control',
+      description: 'Full control over display options with uniform scaffolding across all problems',
     },
     {
       id: 'mastery' as const,
       emoji: '🎓',
       label: 'Mastery Progression',
+      description: 'Skill-based progression with automatic review mixing for pedagogical practice',
     },
   ]
 
+  const currentModeData = modes.find((m) => m.id === currentMode)
+
   return (
-    <div
-      data-component="mode-selector-tabs"
-      className={css({
-        display: 'flex',
-        gap: '0.5rem',
-        borderBottom: '2px solid',
-        borderColor: isDark ? 'gray.600' : 'gray.200',
-        marginBottom: '1.5rem',
-      })}
-    >
-      {modes.map((mode) => {
-        const isActive = currentMode === mode.id
-        return (
-          <button
-            key={mode.id}
-            type="button"
-            data-action={`select-${mode.id}-mode`}
-            data-selected={isActive}
-            onClick={() => onChange(mode.id)}
-            className={css({
-              flex: 1,
-              padding: '1rem 1.5rem',
-              border: 'none',
-              borderBottom: '3px solid',
-              borderBottomColor: isActive ? 'blue.500' : 'transparent',
-              backgroundColor: isActive
-                ? isDark
-                  ? 'gray.700'
-                  : 'white'
-                : isDark
-                  ? 'gray.800'
-                  : 'gray.50',
-              color: isActive
-                ? isDark
-                  ? 'blue.300'
-                  : 'blue.600'
-                : isDark
-                  ? 'gray.400'
-                  : 'gray.600',
-              cursor: 'pointer',
-              transition: 'all 0.2s',
-              fontSize: '0.95rem',
-              fontWeight: isActive ? '700' : '500',
-              display: 'flex',
-              alignItems: 'center',
-              justifyContent: 'center',
-              gap: '0.5rem',
-              borderTopLeftRadius: '8px',
-              borderTopRightRadius: '8px',
-              _hover: {
+    <div data-component="mode-selector-tabs">
+      {/* Tab buttons */}
+      <div
+        className={css({
+          display: 'flex',
+          gap: '0.5rem',
+          borderBottom: '2px solid',
+          borderColor: isDark ? 'gray.600' : 'gray.200',
+        })}
+      >
+        {modes.map((mode) => {
+          const isActive = currentMode === mode.id
+          return (
+            <button
+              key={mode.id}
+              type="button"
+              data-action={`select-${mode.id}-mode`}
+              data-selected={isActive}
+              onClick={() => onChange(mode.id)}
+              className={css({
+                flex: 1,
+                padding: '1rem 1.5rem',
+                border: 'none',
+                borderBottom: '3px solid',
+                borderBottomColor: isActive ? 'blue.500' : 'transparent',
                 backgroundColor: isActive
                   ? isDark
                     ? 'gray.700'
                     : 'white'
                   : isDark
-                    ? 'gray.700'
-                    : 'gray.100',
-                borderBottomColor: isActive ? 'blue.500' : isDark ? 'gray.500' : 'gray.400',
+                    ? 'gray.800'
+                    : 'gray.50',
                 color: isActive
                   ? isDark
                     ? 'blue.300'
                     : 'blue.600'
                   : isDark
-                    ? 'gray.300'
-                    : 'gray.700',
-              },
-            })}
-          >
-            <span className={css({ fontSize: '1.25rem' })}>{mode.emoji}</span>
-            <span>{mode.label}</span>
-          </button>
-        )
-      })}
+                    ? 'gray.400'
+                    : 'gray.600',
+                cursor: 'pointer',
+                transition: 'all 0.2s',
+                fontSize: '0.95rem',
+                fontWeight: isActive ? '700' : '500',
+                display: 'flex',
+                alignItems: 'center',
+                justifyContent: 'center',
+                gap: '0.5rem',
+                borderTopLeftRadius: '8px',
+                borderTopRightRadius: '8px',
+                _hover: {
+                  backgroundColor: isActive
+                    ? isDark
+                      ? 'gray.700'
+                      : 'white'
+                    : isDark
+                      ? 'gray.700'
+                      : 'gray.100',
+                  borderBottomColor: isActive ? 'blue.500' : isDark ? 'gray.500' : 'gray.400',
+                  color: isActive
+                    ? isDark
+                      ? 'blue.300'
+                      : 'blue.600'
+                    : isDark
+                      ? 'gray.300'
+                      : 'gray.700',
+                },
+              })}
+            >
+              <span className={css({ fontSize: '1.25rem' })}>{mode.emoji}</span>
+              <span>{mode.label}</span>
+            </button>
+          )
+        })}
+      </div>
+
+      {/* Description of active mode */}
+      {currentModeData && (
+        <p
+          className={css({
+            fontSize: 'sm',
+            color: isDark ? 'gray.400' : 'gray.600',
+            mt: '3',
+            mb: '3',
+            px: '2',
+            lineHeight: '1.5',
+          })}
+        >
+          {currentModeData.description}
+        </p>
+      )}
     </div>
   )
 }