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-core/src/events.rs

@@ -0,0 +1,74 @@
+//! 工作流事件定义
+
+use serde::{Deserialize, Serialize};
+
+use crate::types::NodeId;
+
+/// 人工审批响应
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct HumanApprovalResponse {
+    pub execution_id: String,
+    pub node_id: NodeId,
+    pub decision: String,
+    pub comment: Option<String>,
+}
+
+/// 工作流事件
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(tag = "type", rename_all = "snake_case")]
+pub enum WorkflowEvent {
+    /// 节点开始执行
+    NodeStarted {
+        node_id: NodeId,
+    },
+    /// 节点执行进度更新
+    NodeProgress {
+        node_id: NodeId,
+        progress: f32,
+        message: String,
+    },
+    /// 节点产生输出
+    NodeOutput {
+        node_id: NodeId,
+        output: String,
+    },
+    /// 节点执行完成
+    NodeCompleted {
+        node_id: NodeId,
+        duration_ms: u64,
+    },
+    /// 节点执行失败
+    NodeFailed {
+        node_id: NodeId,
+        error: String,
+    },
+    /// 工作流暂停（等待外部输入）
+    WorkflowPaused {
+        reason: String,
+        waiting_node: NodeId,
+    },
+    /// 工作流执行完成
+    WorkflowCompleted {
+        total_duration_ms: u64,
+    },
+    /// 工作流执行失败
+    WorkflowFailed {
+        error: String,
+        failed_node: NodeId,
+    },
+    /// 人工审批请求
+    HumanApprovalRequest {
+        execution_id: String,
+        node_id: NodeId,
+        title: String,
+        description: String,
+        options: Vec<String>,
+    },
+    /// 人工审批响应
+    HumanApprovalResponse {
+        execution_id: String,
+        node_id: NodeId,
+        decision: String,
+        comment: Option<String>,
+    },
+}