feat: 英语描红 字母选择修改

miniprogram/englishPages/letterTracing/letterTracing.less

@@ -80,12 +80,6 @@ page {
     padding-left: 8rpx;
 }
 
-.lt-section-body {
-    display: flex;
-    flex-direction: column;
-    gap: 24rpx;
-}
-
 /* ===== 练习类型 2列卡片网格 (grid-cols-2 gap-4) ===== */
 .lt-mode-grid {
     display: grid;
@@ -191,40 +185,6 @@ page {
     color: @text-selected-btn;
 }
 
-/* ===== 展开/收起按钮（UI 稿 rounded-full bg-surface-container-low） ===== */
-.lt-expand-toggle {
-    display: flex;
-    align-items: center;
-    justify-content: center;
-    gap: 8rpx;
-    padding: 12rpx 32rpx;
-    border-radius: 999rpx;
-    background: #f8f0e0;
-    align-self: center;
-    margin: 16rpx auto 0;
-    transition:
-        background-color 0.2s ease,
-        transform 0.2s ease;
-}
-
-.lt-expand-toggle--hover {
-    background: @bg-card;
-    transform: scale(0.96);
-}
-
-.lt-expand-toggle__text {
-    font-size: 28rpx;
-    font-weight: 500;
-    color: @text-secondary;
-    line-height: 1;
-}
-
-.lt-expand-toggle__icon {
-    display: inline-flex;
-    align-items: center;
-    justify-content: center;
-}
-
 /* ===== 大小写切换 / 字母分组选择 ===== */
 .lt-chip-row {
     display: flex;