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/state.rs

@@ -0,0 +1,147 @@
+//! 节点状态机 — 管理节点的状态转换
+//!
+//! 合法转换：Pending → Running，Running → Completed / Failed，
+//! 非法转换返回错误，避免状态被随意覆盖。
+
+use std::collections::HashMap;
+
+use df_core::types::{NodeId, NodeStatus};
+
+/// 节点状态机
+#[derive(Debug, Clone)]
+pub struct StateMachine {
+    /// 节点状态映射
+    states: HashMap<NodeId, NodeStatus>,
+}
+
+impl StateMachine {
+    /// 创建状态机
+    pub fn new() -> Self {
+        Self {
+            states: HashMap::new(),
+        }
+    }
+
+    /// 获取节点状态
+    pub fn get(&self, node_id: &NodeId) -> NodeStatus {
+        self.states
+            .get(node_id)
+            .cloned()
+            .unwrap_or(NodeStatus::Pending)
+    }
+
+    /// 判断状态转换是否合法
+    fn is_legal(from: &NodeStatus, to: &NodeStatus) -> bool {
+        matches!(
+            (from, to),
+            (NodeStatus::Pending, NodeStatus::Running)
+                | (NodeStatus::Running, NodeStatus::Completed)
+                | (NodeStatus::Running, NodeStatus::Failed)
+        )
+    }
+
+    /// 状态转换 — 校验合法性后更新，非法转换返回错误
+    pub fn transition(&mut self, node_id: NodeId, target: NodeStatus) -> anyhow::Result<()> {
+        let current = self.get(&node_id);
+        if !Self::is_legal(&current, &target) {
+            anyhow::bail!(
+                "节点 {} 状态转换非法：{} -> {}",
+                node_id,
+                current.as_str(),
+                target.as_str()
+            );
+        }
+        self.states.insert(node_id, target);
+        Ok(())
+    }
+
+    /// 设置节点为运行中（仅允许 Pending -> Running）
+    pub fn set_running(&mut self, node_id: NodeId) -> anyhow::Result<()> {
+        self.transition(node_id, NodeStatus::Running)
+    }
+
+    /// 设置节点为已完成（仅允许 Running -> Completed）
+    pub fn set_completed(&mut self, node_id: NodeId) -> anyhow::Result<()> {
+        self.transition(node_id, NodeStatus::Completed)
+    }
+
+    /// 设置节点为失败（仅允许 Running -> Failed）
+    pub fn set_failed(&mut self, node_id: NodeId) -> anyhow::Result<()> {
+        self.transition(node_id, NodeStatus::Failed)
+    }
+
+    /// 设置节点为等待中（暂未纳入转换校验）
+    pub fn set_waiting(&mut self, node_id: NodeId) {
+        self.states.insert(node_id, NodeStatus::Waiting);
+    }
+
+    /// 设置节点为已跳过（暂未纳入转换校验）
+    pub fn set_skipped(&mut self, node_id: NodeId) {
+        self.states.insert(node_id, NodeStatus::Skipped);
+    }
+
+    /// 获取所有状态快照
+    pub fn snapshot(&self) -> &HashMap<NodeId, NodeStatus> {
+        &self.states
+    }
+
+    /// 检查节点是否被取消
+    pub fn is_cancelled(&self, node_id: &NodeId) -> bool {
+        matches!(self.get(node_id), NodeStatus::Cancelled)
+    }
+}
+
+impl Default for StateMachine {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_legal_transitions() {
+        let mut sm = StateMachine::new();
+        let id = "node-a".to_string();
+
+        // Pending -> Running -> Completed 全程合法
+        assert!(sm.set_running(id.clone()).is_ok());
+        assert_eq!(sm.get(&id), NodeStatus::Running);
+        assert!(sm.set_completed(id.clone()).is_ok());
+        assert_eq!(sm.get(&id), NodeStatus::Completed);
+
+        // Running -> Failed 合法
+        let id2 = "node-b".to_string();
+        sm.set_running(id2.clone()).unwrap();
+        assert!(sm.set_failed(id2.clone()).is_ok());
+        assert_eq!(sm.get(&id2), NodeStatus::Failed);
+    }
+
+    #[test]
+    fn test_illegal_transitions_rejected() {
+        let mut sm = StateMachine::new();
+        let id = "node-a".to_string();
+
+        // Pending -> Completed 非法
+        let err = sm.set_completed(id.clone()).unwrap_err();
+        assert!(err.to_string().contains("状态转换非法"));
+        assert!(err.to_string().contains("node-a"));
+        // 状态保持不变
+        assert_eq!(sm.get(&id), NodeStatus::Pending);
+
+        // Pending -> Failed 非法
+        assert!(sm.set_failed(id.clone()).is_err());
+
+        // Completed 为终态，不允许再转 Running
+        sm.set_running(id.clone()).unwrap();
+        sm.set_completed(id.clone()).unwrap();
+        assert!(sm.set_running(id.clone()).is_err());
+
+        // Running -> Running 重复置位非法
+        let id2 = "node-b".to_string();
+        sm.set_running(id2.clone()).unwrap();
+        assert!(sm.set_running(id2.clone()).is_err());
+    }
+}