优化: df-ai/df-storage/df-nodes 底层加固: 上下文/模型/节点/仓储

df-ai:
- context/mod.rs + manager_tests.rs: 上下文管理调整 + 测试同步(48 行)
- openai_compat.rs: OpenAI 兼容层增强(+51)
- presets/models.json: 模型预设 +18

df-storage:
- crud/conversation_repo.rs: 会话仓储(loop_state 相关)
- crud/task_repo.rs: 任务仓储
- crud/mod.rs: 导出调整

df-nodes:
- task_advance_node.rs: 任务推进节点

验收: cargo check -p devflow EXIT 0。

crates/df-storage/src/crud/conversation_repo.rs

@@ -1094,4 +1094,43 @@ mod tests {
             .expect("snapshot");
         assert_eq!(snapshot, r#"[{"seq":0}]"#, "冲突时应保留首次快照");
     }
+
+    /// #904 契约:set_loop_state 写 "parked" 后 get_by_id 可读回(停靠出口写侧单点)。
+    /// 锁死「停靠状态写入收敛进 emit_task_parked」依赖的 repo 能力——若 set_loop_state
+    /// 或 from_row 的 loop_state 映射回归,停靠卡「继续」将再次撞「AI 未在暂停态」。
+    #[tokio::test]
+    async fn set_loop_state_parked_roundtrip() {
+        let db = Database::open_in_memory().await.expect("open_in_memory");
+        let repo = AiConversationRepo::new(&db);
+        repo.insert(AiConversationRecord {
+            id: "c1".into(),
+            title: None,
+            messages: "[]".into(),
+            provider_id: None,
+            model: None,
+            models: None,
+            archived: false,
+            pinned: false,
+            prompt_tokens: Some(0),
+            completion_tokens: Some(0),
+            pinned_goals: None,
+            pending_approvals: None,
+            created_at: "0".into(),
+            updated_at: "0".into(),
+            origin: None,
+            boundary_json: None,
+            loop_state: None,
+        })
+        .await
+        .expect("insert");
+
+        assert!(repo.set_loop_state("c1", Some("parked")).await.expect("set"));
+        let got = repo.get_by_id("c1").await.expect("get").expect("row");
+        assert_eq!(got.loop_state.as_deref(), Some("parked"), "写 parked 应可读回");
+
+        // 清态(running 收敛出口)可读回 None
+        assert!(repo.set_loop_state("c1", None).await.expect("clear"));
+        let cleared = repo.get_by_id("c1").await.expect("get").expect("row");
+        assert_eq!(cleared.loop_state, None, "清 loop_state 应可读回 None");
+    }
 }

crates/df-storage/src/crud/mod.rs

@@ -72,6 +72,7 @@ macro_rules! impl_repo {
         update  => |$u_conn:ident, $u_rec:ident| $update_body:expr
     ) => {
         $(#[$meta])*
+        #[derive(Clone)]
         pub struct $name {
             conn: Arc<Mutex<Connection>>,
         }

crates/df-storage/src/crud/task_repo.rs

@@ -249,6 +249,34 @@ impl TaskRepo {
         .map_err(storage_err)?
     }
 
+    /// 判定任务是否在回收站(soft_delete 已设 deleted_at)。
+    ///
+    /// 专供推进链 CAS 失败后的**原因区分**:`advance_status_atomic` 的 CAS SQL 带
+    /// `deleted_at IS NULL` 条件,软删任务必然 affected==0 返回 None;调用方据此
+    /// 回查本方法,把「已变更(并发推进或旁路修改)」这个误导性错误,精确改写为
+    /// 「任务在回收站」,让 LLM/用户知道该先恢复而非重试。
+    ///
+    /// 返回 true = 任务存在且 deleted_at 非 NULL(在回收站);false = 不存在或未删。
+    /// 单列轻查询(SELECT 1),不拉全记录,失败回查开销可忽略。
+    pub async fn is_deleted(&self, id: &str) -> Result<bool> {
+        let conn = self.conn.clone();
+        let id = id.to_owned();
+        tokio::task::spawn_blocking(move || {
+            let guard = conn.blocking_lock();
+            let mut stmt = guard
+                .prepare("SELECT 1 FROM tasks WHERE id = ?1 AND deleted_at IS NOT NULL")
+                .map_err(storage_err)?;
+            let found = stmt
+                .query_row(params![id], |_| Ok(()))
+                .optional()
+                .map_err(storage_err)?
+                .is_some();
+            Ok(found)
+        })
+        .await
+        .map_err(storage_err)?
+    }
+
     /// 按 id 查未删除任务(`WHERE id AND deleted_at IS NULL`)。
     ///
     /// 专供 [`validate_parent_id`](super::task_validation) 的父任务存在性检查: