fix(popup): 新建知识库弹窗点击即关闭 + Cancel 按钮无法关闭弹窗

根因(核实 bricks/popup.js 源码):
1. popup_options 显式写了 auto_dismiss:true，Popup 构造时把 click 绑到整个 bricks.Body，
   而 click_outside 只判断 event.target != this.dom_element(无子树 contains 判定)，
   点击弹窗内任何子元素(输入框/下拉/按钮)都命中 → 立即 dismiss。改为 auto_dismiss:false。
2. 加 dismiss_events:['cancel','submited'] 让 Form 的取消/提交完成关闭弹窗。
   但 set_dismiss_events 只绑 load_content 返回的根 widget，而 dispatch 用
   new Event() 不冒泡(bubbles:false) —— 原根节点是 VBox、事件由子 Form 发出，绑不上。
   故把 Form 提为 new_kb_form.ui 根 widget，标题改用 Form 自带 title 选项。
   (title 不是 Popup 的合法 option，仅 PopupWindow/Form 支持)

wwwroot/knowledge_bases_list/index.ui

@@ -63,7 +63,11 @@
                                     "actiontype": "urlwidget",
                                     "target": "Popup",
                                     "popup_options": {
-                                        "auto_dismiss": true
+                                        "auto_dismiss": false,
+                                        "dismiss_events": ["cancel", "submited"],
+                                        "movable": true,
+                                        "width": "34%",
+                                        "height": "auto"
                                     },
                                     "options": {
                                         "url": "{{entire_url('./new_kb_form.ui')}}"

wwwroot/knowledge_bases_list/new_kb_form.ui

@@ -1,24 +1,19 @@
 {
-    "widgettype": "VBox",
-    "options": {"padding": "16px", "spacing": "12px"},
-    "subwidgets": [
-        {"widgettype": "Text", "options": {"text": "新建知识库", "cfontsize": 18, "fontWeight": "bold"}},
-        {
-            "widgettype": "Form",
-            "id": "kb_form",
-            "options": {
-                "cols": 1,
-                "fields": [
-                    {"name": "name", "label": "名称", "uitype": "str", "required": true},
-                    {"name": "description", "label": "描述", "uitype": "text"},
-                    {"name": "embedding_type", "label": "向量引擎", "uitype": "code", "value": "clip-vith14", "dataurl": "{{entire_url('./embedding_options.dspy')}}"}
-                ]
-            }
-        }
-    ],
+    "widgettype": "Form",
+    "id": "kb_form",
+    "options": {
+        "cols": 1,
+        "title": "新建知识库",
+        "padding": "16px",
+        "fields": [
+            {"name": "name", "label": "名称", "uitype": "str", "required": true},
+            {"name": "description", "label": "描述", "uitype": "text"},
+            {"name": "embedding_type", "label": "向量引擎", "uitype": "code", "value": "clip-vith14", "dataurl": "{{entire_url('./embedding_options.dspy')}}"}
+        ]
+    },
     "binds": [
         {
-            "wid": "kb_form",
+            "wid": "self",
             "event": "submit",
             "actiontype": "urlwidget",
             "target": "app.rag_main_content",