✨ feat(sql-files): 支持外部 SQL 目录树与双击打开

- 新增 SQL 目录选择、枚举与按路径读取接口，复用大文件执行能力
- Sidebar 增加外部 SQL 文件目录树、目录管理入口与双击打开查询标签
- 补充 external SQL 持久化与前后端回归测试

Fixes #319

frontend/src/utils/externalSqlTree.ts

@@ -0,0 +1,131 @@
+import type { ExternalSQLDirectory, ExternalSQLTreeEntry } from '../types';
+
+export type ExternalSQLNodeType =
+  | 'external-sql-root'
+  | 'external-sql-directory'
+  | 'external-sql-folder'
+  | 'external-sql-file';
+
+export interface ExternalSQLTreeNode {
+  title: string;
+  key: string;
+  isLeaf?: boolean;
+  children?: ExternalSQLTreeNode[];
+  type: ExternalSQLNodeType;
+  dataRef: Record<string, unknown>;
+}
+
+type BuildExternalSQLRootNodeParams = {
+  dbNodeKey: string;
+  connectionId: string;
+  dbName: string;
+  directories: ExternalSQLDirectory[];
+  directoryTrees: Record<string, ExternalSQLTreeEntry[]>;
+};
+
+const normalizeExternalSQLPath = (value: string): string =>
+  String(value || '').trim().replace(/\\/g, '/');
+
+const resolveDirectoryDisplayName = (directory: ExternalSQLDirectory): string => {
+  const explicitName = String(directory.name || '').trim();
+  if (explicitName) return explicitName;
+  const normalizedPath = normalizeExternalSQLPath(directory.path);
+  const segments = normalizedPath.split('/').filter(Boolean);
+  return segments[segments.length - 1] || 'SQL目录';
+};
+
+export const buildExternalSQLDirectoryId = (connectionId: string, dbName: string, directoryPath: string): string =>
+  `external-sql-dir:${String(connectionId || '').trim()}:${String(dbName || '').trim()}:${normalizeExternalSQLPath(directoryPath)}`;
+
+export const buildExternalSQLTabId = (connectionId: string, dbName: string, filePath: string): string =>
+  `external-sql-tab:${String(connectionId || '').trim()}:${String(dbName || '').trim()}:${normalizeExternalSQLPath(filePath)}`;
+
+const buildExternalSQLNodeKey = (type: ExternalSQLNodeType, base: string): string =>
+  `${type}:${normalizeExternalSQLPath(base)}`;
+
+const mapExternalSQLTreeEntries = (
+  entries: ExternalSQLTreeEntry[],
+  context: { connectionId: string; dbName: string; dbNodeKey: string; directoryId: string },
+): ExternalSQLTreeNode[] => entries.map((entry) => {
+  const entryPath = normalizeExternalSQLPath(entry.path);
+  if (entry.isDir) {
+    const children = mapExternalSQLTreeEntries(entry.children || [], context);
+    return {
+      title: entry.name,
+      key: buildExternalSQLNodeKey('external-sql-folder', entryPath),
+      type: 'external-sql-folder',
+      isLeaf: children.length === 0,
+      children: children.length > 0 ? children : undefined,
+      dataRef: {
+        connectionId: context.connectionId,
+        dbName: context.dbName,
+        dbNodeKey: context.dbNodeKey,
+        directoryId: context.directoryId,
+        path: entry.path,
+        name: entry.name,
+      },
+    };
+  }
+
+  return {
+    title: entry.name,
+    key: buildExternalSQLNodeKey('external-sql-file', entryPath),
+    type: 'external-sql-file',
+    isLeaf: true,
+    dataRef: {
+      connectionId: context.connectionId,
+      dbName: context.dbName,
+      dbNodeKey: context.dbNodeKey,
+      directoryId: context.directoryId,
+      path: entry.path,
+      name: entry.name,
+    },
+  };
+});
+
+export const buildExternalSQLRootNode = ({
+  dbNodeKey,
+  connectionId,
+  dbName,
+  directories,
+  directoryTrees,
+}: BuildExternalSQLRootNodeParams): ExternalSQLTreeNode => {
+  const sortedDirectories = [...directories].sort((left, right) =>
+    resolveDirectoryDisplayName(left).toLowerCase().localeCompare(resolveDirectoryDisplayName(right).toLowerCase()),
+  );
+
+  const children = sortedDirectories.map((directory) => {
+    const directoryChildren = mapExternalSQLTreeEntries(directoryTrees[directory.id] || [], {
+      connectionId,
+      dbName,
+      dbNodeKey,
+      directoryId: directory.id,
+    });
+    return {
+      title: resolveDirectoryDisplayName(directory),
+      key: buildExternalSQLNodeKey('external-sql-directory', directory.id),
+      type: 'external-sql-directory' as const,
+      isLeaf: directoryChildren.length === 0,
+      children: directoryChildren.length > 0 ? directoryChildren : undefined,
+      dataRef: {
+        ...directory,
+        connectionId,
+        dbName,
+        dbNodeKey,
+      },
+    };
+  });
+
+  return {
+    title: children.length > 0 ? `外部 SQL 文件 (${children.length})` : '外部 SQL 文件',
+    key: `${dbNodeKey}-external-sql`,
+    type: 'external-sql-root',
+    isLeaf: children.length === 0,
+    children: children.length > 0 ? children : undefined,
+    dataRef: {
+      connectionId,
+      dbName,
+      dbNodeKey,
+    },
+  };
+};