fix: 澄清卡片 allow_custom 时允许纯自定义输入提交

- canSubmit 逻辑重构：纯文本卡片只需 customText 非空
- 有选项卡片：满足最小选择数，或（allow_custom 且 customText 非空）即可提交
- 修复其他，请简单描述输入自定义内容后提交按钮灰显的问题

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

mini-program/src/components/ClarificationCard.vue

@@ -63,10 +63,14 @@ const isSingle = computed(() => props.card.card_type === 'single_select')
 const isMulti = computed(() => props.card.card_type === 'multi_select' || props.card.card_type === 'mixed')
 
 const canSubmit = computed(() => {
+  // 纯文本输入卡片：只需 customText 非空
+  if (isTextInput.value) return customText.value.trim().length > 0
+
+  // 有选项的卡片：满足最小选择数，或（允许自定义且 customText 非空）
   const minSel = props.card.min_selections || 1
-  if (selectedValues.value.length < minSel) return false
+  if (selectedValues.value.length >= minSel) return true
-  if (isTextInput.value && !customText.value.trim()) return false
+  if (props.card.allow_custom && customText.value.trim()) return true
-  return true
+  return false
 })
 
 function isSelected(value) {