fix: 禁用层级拖动并移除相关UI控制

禁用useThinkFlow中的hierarchicalDragging选项以解决拖动行为问题，同时移除TopNav中对应的控制按钮以保持UI一致性

src/components/TopNav.vue

@@ -146,16 +146,6 @@ const callAndClose = (fn: () => void) => {
                     <span>{{ props.t('nav.center') }}</span>
                 </button>
 
-                <button
-                    @click="props.config.hierarchicalDragging = !props.config.hierarchicalDragging"
-                    class="toolbar-btn flex-shrink-0"
-                    :class="props.config.hierarchicalDragging ? 'text-orange-500 bg-orange-50 border-orange-100' : 'text-slate-400 hover:text-slate-600'"
-                    :title="props.t('nav.hierarchicalDragging')"
-                >
-                    <ArrowLeftRight class="w-3.5 h-3.5 md:w-4 h-4" />
-                    <span>{{ props.t('nav.hierarchicalDragging') }}</span>
-                </button>
-
                 <div class="h-4 w-[1px] bg-slate-100 mx-1 flex-shrink-0"></div>
 
                 <button @click="props.onGenerateSummary" class="toolbar-btn text-orange-600 hover:bg-orange-50 border-orange-100 flex-shrink-0" :title="props.t('nav.summary')">

src/composables/useThinkFlow.ts

@@ -390,7 +390,7 @@ export function useThinkFlow({ t, locale }: { t: Translate; locale: Ref<string>
                   backgroundVariant: BackgroundVariant.Lines,
                   showControls: true,
                   showMiniMap: true,
-                  hierarchicalDragging: true,
+                  hierarchicalDragging: false,
                   snapToGrid: true,
                   snapGrid: [16, 16] as [number, number],
                   snapToAlignment: true,