新增: 项目状态机分层+任务状态枚举合并

真分层(df-project):
- ProjectManager 加 can_transition/transition/is_terminal 状态机
- 创建加 EmptyName 校验,返回 Result 而非裸实体
- 新增 ProjectTransitionError 三种错误变体
- 调用方(idea.rs promote_idea)适配 Result 传播

双源合并:
- TaskStatus::as_str 改为 const fn(允许 const 上下文调用)
- task_state_machine 字符串常量从 TaskStatus enum 派生
- IdeaStatus/ProjectStatus as_str 同步改为 const fn(一致性)

架构债设计方案:
- #8 IPC 错误结构化迁移路径(IpcError enum + 前端消费)
- #15 AI 状态机抽离 df-ai-session(4 阶段)
- #18 配置四源统一(AppConfig 单例 + 环境变量覆盖)
- #19 SQLite 连接池(r2d2)

crates/df-project/Cargo.toml

@@ -11,3 +11,4 @@ tokio = { workspace = true }
 anyhow = { workspace = true }
 chrono = { workspace = true }
 tracing = { workspace = true }
+thiserror = { workspace = true }

crates/df-project/src/manager.rs

@@ -1,4 +1,10 @@
-//! 项目管理器 — 项目的 CRUD 与生命周期管理
+//! 项目管理器 — 项目的领域层(CRUD 构造 + 状态机 + 业务约束)
+//!
+//! 任务 #16 真分层:本 crate 不再只是"构造实体的工厂函数",而是承载项目领域规则。
+//! Storage 层(df-storage::ProjectRepo)仅负责持久化,状态合法性 / 业务约束在此。
+//!
+//! 调用方(src-tauri commands/project.rs)推进项目状态时必须经
+//! `ProjectManager::can_transition` / `transition` 校验,防非法跳态。
 
 use serde::{Deserialize, Serialize};
 
@@ -39,15 +45,32 @@ pub struct CreateProjectInput {
     pub tags: Vec<String>,
 }
 
-/// 项目管理器
+/// 项目状态机错误
+#[derive(Debug, thiserror::Error)]
+pub enum ProjectTransitionError {
+    #[error("项目状态转换非法: {from:?} → {to:?}")]
+    IllegalTransition {
+        from: ProjectStatus,
+        to: ProjectStatus,
+    },
+    #[error("项目名称不能为空")]
+    EmptyName,
+    #[error("项目已处在终态 {0:?},不可再推进")]
+    TerminalState(ProjectStatus),
+}
+
+/// 项目管理器(无状态纯逻辑,实体构造 + 状态机 + 业务约束)
 pub struct ProjectManager;
 
 impl ProjectManager {
     /// 创建新项目 — 构造领域实体(不落库);持久化由调用方经 storage 层 ProjectRecord 映射完成
     /// (见 commands/idea.rs::promote_idea)。领域层不依赖 storage,保持分层。
-    pub fn create(input: CreateProjectInput) -> Project {
+    pub fn create(input: CreateProjectInput) -> Result<Project, ProjectTransitionError> {
+        if input.name.trim().is_empty() {
+            return Err(ProjectTransitionError::EmptyName);
+        }
         let now = chrono::Utc::now();
-        Project {
+        Ok(Project {
             id: df_types::types::new_id(),
             name: input.name,
             description: input.description,
@@ -57,11 +80,15 @@ impl ProjectManager {
             tags: input.tags,
             created_at: now,
             updated_at: now,
-        }
+        })
     }
 
     /// 从想法创建项目
-    pub fn create_from_idea(name: String, description: String, idea_id: IdeaId) -> Project {
+    pub fn create_from_idea(
+        name: String,
+        description: String,
+        idea_id: IdeaId,
+    ) -> Result<Project, ProjectTransitionError> {
         Self::create(CreateProjectInput {
             name,
             description,
@@ -71,4 +98,118 @@ impl ProjectManager {
         })
     }
 
+    /// 判断项目状态转换是否合法(状态机核心)。
+    ///
+    /// 项目状态语义(与 ARCHITECTURE.md 一致):
+    ///   - Planning   → InProgress(开始), Cancelled(取消)
+    ///   - InProgress → Testing(提交测试), Paused(暂停), Cancelled
+    ///   - Testing    → Completed(测试通过), InProgress(退回开发), Cancelled
+    ///   - Completed  → 终态(不可变)
+    ///   - Paused     → InProgress(恢复), Cancelled
+    ///   - Cancelled  → 终态
+    pub fn can_transition(from: &ProjectStatus, to: &ProjectStatus) -> bool {
+        use ProjectStatus::*;
+        matches!((from, to),
+            (Planning, InProgress) | (Planning, Cancelled)
+            | (InProgress, Testing) | (InProgress, Paused) | (InProgress, Cancelled)
+            | (Testing, Completed) | (Testing, InProgress) | (Testing, Cancelled)
+            | (Paused, InProgress) | (Paused, Cancelled)
+        )
+    }
+
+    /// 执行状态转换,返回新状态或非法错误。
+    ///
+    /// 调用方(如 IPC `update_project_status` / `advance_project`)应用本方法校验后
+    /// 再写 storage,防跳态(如 Planning → Completed 跳过 Testing)。
+    pub fn transition(
+        from: ProjectStatus,
+        to: ProjectStatus,
+    ) -> Result<ProjectStatus, ProjectTransitionError> {
+        if !Self::can_transition(&from, &to) {
+            // 区分错误: 终态→任何 vs 一般非法
+            if matches!(from, ProjectStatus::Completed | ProjectStatus::Cancelled) {
+                return Err(ProjectTransitionError::TerminalState(from));
+            }
+            return Err(ProjectTransitionError::IllegalTransition { from, to });
+        }
+        Ok(to)
+    }
+
+    /// 是否为终态(不可再转换)
+    pub fn is_terminal(s: &ProjectStatus) -> bool {
+        matches!(s, ProjectStatus::Completed | ProjectStatus::Cancelled)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn create_rejects_empty_name() {
+        let err = ProjectManager::create(CreateProjectInput {
+            name: "  ".into(),
+            description: String::new(),
+            idea_id: None,
+            priority: Priority::default(),
+            tags: vec![],
+        }).unwrap_err();
+        assert!(matches!(err, ProjectTransitionError::EmptyName));
+    }
+
+    #[test]
+    fn main_path_planning_to_completed() {
+        use ProjectStatus::*;
+        assert!(ProjectManager::can_transition(&Planning, &InProgress));
+        assert!(ProjectManager::can_transition(&InProgress, &Testing));
+        assert!(ProjectManager::can_transition(&Testing, &Completed));
+    }
+
+    #[test]
+    fn illegal_skips_rejected() {
+        use ProjectStatus::*;
+        assert!(!ProjectManager::can_transition(&Planning, &Completed));
+        assert!(!ProjectManager::can_transition(&Planning, &Testing));
+        assert!(!ProjectManager::can_transition(&InProgress, &Completed));
+    }
+
+    #[test]
+    fn terminal_states_block_all() {
+        use ProjectStatus::*;
+        for term in [Completed, Cancelled] {
+            for to in [Planning, InProgress, Testing, Paused] {
+                assert!(!ProjectManager::can_transition(&term, &to));
+            }
+        }
+    }
+
+    #[test]
+    fn paused_round_trip() {
+        use ProjectStatus::*;
+        assert!(ProjectManager::can_transition(&InProgress, &Paused));
+        assert!(ProjectManager::can_transition(&Paused, &InProgress));
+    }
+
+    #[test]
+    fn transition_returns_target_on_legal() {
+        use ProjectStatus::*;
+        assert_eq!(
+            ProjectManager::transition(Planning, InProgress).unwrap(),
+            InProgress
+        );
+    }
+
+    #[test]
+    fn transition_errors_on_illegal() {
+        use ProjectStatus::*;
+        let err = ProjectManager::transition(Planning, Completed).unwrap_err();
+        assert!(matches!(err, ProjectTransitionError::IllegalTransition { .. }));
+    }
+
+    #[test]
+    fn transition_errors_on_terminal_source() {
+        use ProjectStatus::*;
+        let err = ProjectManager::transition(Completed, InProgress).unwrap_err();
+        assert!(matches!(err, ProjectTransitionError::TerminalState(_)));
+    }
 }