feat: 优化知识库分块操作区与滚动导航

- 将向量化操作上移到分块预览前的统一操作区

- 增加页顶页末双气泡并完善边界禁用状态

easyflow-ui-admin/app/src/views/ai/documentCollection/SegmenterDoc.vue

@@ -432,19 +432,7 @@ watch(
       </div>
     </ElForm>
 
-    <section class="workbench__content">
-      <SplitterDocPreview
-        :loading="previewLoading"
-        :preview-items="previewItems"
-        @preview-session-change="handlePreviewSessionChange"
-      />
-    </section>
-
-    <div v-if="previewError" class="workbench__error">
-      {{ previewError }}
-    </div>
-
-    <div class="workbench__footer">
+    <div class="workbench__actions">
       <ElButton :disabled="startLoading" @click="handleCancel">
         {{ $t('button.cancel') }}
       </ElButton>
@@ -457,6 +445,18 @@ watch(
         {{ $t('button.startIndex') }}
       </ElButton>
     </div>
+
+    <section class="workbench__content">
+      <SplitterDocPreview
+        :loading="previewLoading"
+        :preview-items="previewItems"
+        @preview-session-change="handlePreviewSessionChange"
+      />
+    </section>
+
+    <div v-if="previewError" class="workbench__error">
+      {{ previewError }}
+    </div>
   </div>
 </template>
 
@@ -484,6 +484,15 @@ watch(
   grid-column: 1 / -1;
 }
 
+.workbench__actions {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 8px;
+  justify-content: flex-end;
+  padding-bottom: 16px;
+  border-bottom: 1px solid var(--el-border-color-lighter);
+}
+
 .workbench__content {
   min-height: 620px;
 }
@@ -500,22 +509,6 @@ watch(
   border-radius: 16px;
 }
 
-.workbench__footer {
-  position: sticky;
-  bottom: 0;
-  display: flex;
-  justify-content: flex-end;
-  gap: 12px;
-  padding: 16px 0 8px;
-  margin-top: auto;
-  background: linear-gradient(
-    180deg,
-    rgb(246 248 251 / 0%) 0%,
-    rgb(246 248 251 / 82%) 30%,
-    rgb(246 248 251 / 100%) 100%
-  );
-}
-
 :deep(.el-form-item__label) {
   padding-bottom: 6px;
   font-size: 13px;