chore: 初始化 BlockFlow Workbench 仓库

建立前端与 Tauri 桌面端的首个版本提交，包含核心编辑器、项目文件读写、测试与构建配置。

补充 Git 忽略规则和换行规范，排除依赖、构建产物、本地运行日志与临时验证文件，方便在其他电脑继续开发。

src/project/fileSystem.ts

@@ -0,0 +1,22 @@
+export type DirectoryEntry = {
+  name: string
+  path: string
+  type: "file" | "directory"
+}
+
+export type ProjectFileSystem = {
+  readText(filePath: string): Promise<string>
+  writeText(filePath: string, content: string): Promise<void>
+  mkdir(dirPath: string): Promise<void>
+  readdir(dirPath: string): Promise<DirectoryEntry[]>
+  exists(filePath: string): Promise<boolean>
+  stat(filePath: string): Promise<{ type: "file" | "directory" }>
+}
+
+export function requireProjectFileSystem(fs: ProjectFileSystem | undefined): ProjectFileSystem {
+  if (fs === undefined) {
+    throw new Error("A ProjectFileSystem adapter is required.")
+  }
+
+  return fs
+}