refactor(ui): 拆分 app/connection_view/widgets 为子组件，对话框归拢 dialogs/

- ui/app/ 拆为门面、events(引擎事件泵)、actions(用户动作)、io(导入导出)、
  theme(主题)、titlebar/sidebar/main_area(渲染分区)
- ui/connection_view/ 拆为门面、subscribe、messages、publish、vars、util(纯函数)
- ui/widgets/ 拆为 select(可搜索下拉)、kv_editor、common(字段行/状态/时间)
- 五个对话框归拢 ui/dialogs/，linear-theme.json 随 theme.rs 迁入 ui/app/
- clippy 0 警告，全部路径经门面保持稳定

gpui-app/src/ui/widgets/select.rs

@@ -0,0 +1,91 @@
+//! 可搜索的枚举下拉：选项模型、委托与统一外观的 Select 包装。
+
+use gpui_kit::component::searchable_list::{ SearchableListDelegate, SearchableListItem };
+use gpui_kit::component::select::{ Select, SelectState };
+use gpui_kit::component::IndexPath;
+use gpui_kit::{ Entity, SharedString, Window };
+
+#[derive(Clone)]
+pub struct OptionItem {
+    pub value: usize,
+    pub label: SharedString,
+}
+
+impl SearchableListItem for OptionItem {
+    type Value = usize;
+    fn title(&self) -> SharedString {
+        self.label.clone()
+    }
+    fn value(&self) -> &usize {
+        &self.value
+    }
+}
+
+#[derive(Clone)]
+pub struct OptionDelegate {
+    pub items: Vec<OptionItem>,
+}
+
+impl OptionDelegate {
+    pub fn new(labels: &[&str]) -> Self {
+        Self {
+            items: labels
+                .iter()
+                .enumerate()
+                .map(|(i, l)| OptionItem {
+                    value: i,
+                    label: (*l).into(),
+                })
+                .collect(),
+        }
+    }
+}
+
+impl SearchableListDelegate for OptionDelegate {
+    type Item = OptionItem;
+    fn items_count(&self, _section: usize) -> usize {
+        self.items.len()
+    }
+    fn item(&self, ix: IndexPath) -> Option<&Self::Item> {
+        self.items.get(ix.row)
+    }
+    fn position<V>(&self, _value: &V) -> Option<IndexPath>
+    where
+        Self::Item: SearchableListItem<Value = V>,
+        V: PartialEq,
+    {
+        // 选中项统一通过 IndexPath 构造，无需按值反查
+        None
+    }
+}
+
+/// 创建字符串枚举下拉状态（在任意实体上下文里调用）。
+pub fn make_select<C: gpui_kit::AppContext>(
+    labels: &[&str],
+    selected: usize,
+    window: &mut Window,
+    cx: &mut C,
+) -> Entity<SelectState<OptionDelegate>> {
+    let selected = selected.min(labels.len().saturating_sub(1));
+    cx.new(|cx| {
+        SelectState::new(
+            OptionDelegate::new(labels),
+            Some(IndexPath::new(selected)),
+            window,
+            cx,
+        )
+    })
+}
+
+// ─── 字段行 ──────────────────────────────────────────────────────────────────
+
+
+/// Select::new 的包装，统一外观。
+pub fn select_element<D: SearchableListDelegate>(
+    state: &Entity<SelectState<D>>,
+) -> Select<D>
+where
+    <D::Item as SearchableListItem>::Value: PartialEq + Clone,
+{
+    Select::new(state)
+}