feat(editing-planner): 标题预设按钮改为方形T字预览样式 + CSS更新

- 预设只绑定样式属性（粗细、描边、阴影、字号），不绑定字体家族
- 按钮用T字母展示实际效果（font-weight/stroke/shadow/fontSize）
- 选中态用高亮外框+背景标识
- 新增默认/经典/醒目/柔和4个预设
- CSS: 方形按钮布局(48px高)、T字预览、小标签、active高亮态

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

apps/web/src/pages/editing-planner/EditingPlanner.css

@@ -1194,7 +1194,7 @@
   color: var(--primary, #6366f1);
 }
 
-/* 标题预设样式按钮 */
+/* 标题预设样式按钮 — 方形 T 字预览 */
 .ep-title-presets {
   display: flex;
   gap: 8px;
@@ -1202,28 +1202,47 @@
 
 .ep-title-preset-btn {
   flex: 1;
-  height: 36px;
+  min-width: 44px;
+  height: 48px;
   background: var(--bg-primary, #ffffff);
-  border: 1px solid var(--border-color, #e2e8f0);
+  border: 2px solid var(--border-color, #e2e8f0);
   border-radius: var(--radius-xs, 8px);
-  color: var(--text-secondary, #64748b);
-  font-size: 12px;
+  color: var(--text-primary, #1e293b);
   cursor: pointer;
   display: flex;
+  flex-direction: column;
   align-items: center;
   justify-content: center;
-  gap: 4px;
-  transition: all 0.2s ease;
+  gap: 2px;
+  padding: 4px 6px;
+  transition: all 0.15s ease;
 }
 
 .ep-title-preset-btn:hover {
   border-color: var(--primary, #6366f1);
-  color: var(--primary, #6366f1);
   background: var(--primary-soft, #eef2ff);
 }
 
-.ep-title-preset-icon {
-  font-size: 14px;
+.ep-title-preset-btn.active {
+  border-color: var(--primary, #6366f1);
+  background: var(--primary-soft, #eef2ff);
+  box-shadow: 0 0 0 1px var(--primary, #6366f1);
+}
+
+.ep-title-preset-t {
+  line-height: 1;
+  font-family: inherit;
+}
+
+.ep-title-preset-label {
+  font-size: 10px;
+  color: var(--text-tertiary, #94a3b8);
+  line-height: 1;
+}
+
+.ep-title-preset-btn.active .ep-title-preset-label {
+  color: var(--primary, #6366f1);
+  font-weight: 500;
 }
 
 /* AI推荐按钮 */