新增: 初始化 DevFlow 项目仓库

Tauri 2 + Vue 3 + Vite 6 桌面应用，Rust workspace 含 13 个 crate
(df-ai / df-storage / df-workflow / df-core / df-execute 等)。
核心能力：AI 聊天 agentic 循环(工具调用+人工审批)、工作流引擎、
任务/想法/项目/阶段管理、可追溯性，及配套前端组件。

crates/df-workflow/src/eventbus.rs

@@ -0,0 +1,68 @@
+//! 事件总线 — 基于 tokio::sync::broadcast 的发布/订阅
+
+use tokio::sync::broadcast;
+use tokio::sync::broadcast::error::SendError;
+use df_core::events::{WorkflowEvent, HumanApprovalResponse};
+
+/// 事件总线
+#[derive(Debug)]
+pub struct EventBus {
+    sender: broadcast::Sender<WorkflowEvent>,
+}
+
+/// 事件订阅者
+pub type EventSubscriber = broadcast::Receiver<WorkflowEvent>;
+
+/// 默认事件通道容量
+const DEFAULT_CAPACITY: usize = 256;
+
+impl EventBus {
+    /// 创建事件总线
+    pub fn new() -> Self {
+        let (sender, _) = broadcast::channel(DEFAULT_CAPACITY);
+        Self { sender }
+    }
+
+    /// 创建指定容量的事件总线
+    pub fn with_capacity(capacity: usize) -> Self {
+        let (sender, _) = broadcast::channel(capacity);
+        Self { sender }
+    }
+
+    /// 发送事件
+    pub async fn send(&self, event: WorkflowEvent) {
+        // broadcast::send 是同步的，忽略接收者已关闭的错误
+        let _ = self.sender.send(event);
+    }
+
+    /// 订阅事件
+    pub fn subscribe(&self) -> EventSubscriber {
+        self.sender.subscribe()
+    }
+
+    /// 发送人工审批请求
+    pub fn emit_human_approval_request(&self, event: WorkflowEvent) -> Result<usize, SendError<WorkflowEvent>> {
+        self.sender.send(event)
+    }
+
+    /// 尝试获取人工审批响应（简化版本，实际需要实现状态存储）
+    pub fn try_recv_human_approval(&self, _execution_id: &str, _node_id: &str) -> Option<HumanApprovalResponse> {
+        // TODO: 实现审批响应的存储和检索
+        // 目前返回 None，需要配合前端实现
+        None
+    }
+}
+
+impl Default for EventBus {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl Clone for EventBus {
+    fn clone(&self) -> Self {
+        Self {
+            sender: self.sender.clone(),
+        }
+    }
+}