重构: 后端 df-ai/commands 拆分+df-nodes/workflow 改造+P0 bug 修复

- df-ai: context 历史中毒三档自愈 sanitize_messages(AC3)+anthropic_compat tool_use_id None 跳过(AC1/AC2)+删 router/stream 死码
- df-core: events 加 select_type+decisions 多选审批契约(F-260615-01)
- df-execute: shell run_command 工具复用(F-260615-05)
- df-nodes: human_node 多选校验+2 端到端测(F-01)+取消跳 set_failed(B-03b-R1/R2/R8)
- df-workflow: executor/dag/state cancel 闭环(B-06/07/03a/b)+provider approve options(R-PD-5)
- df-storage: find_path_conflict 抽公共(R-PD-11)+COLS 常量断言
- df-ideas: 删 IdeaPromoter/PromotionPolicy 死码(R-PD-14)
- src-tauri/commands/ai: secret keyring 迁移(FR-S1/R-PD-4)+GeneratingGuard RAII+disarm(B-09/26)+newConversation 软复位(B-10)+stream 心跳/stop select/空回复判错(B-02/04/05/15)+run_command(F-05)+mask audit(AR-3)
- src-tauri/commands/{project,task,workflow,mod,lib,state}: task detail IPC(F-02)+approve decisions+task list 联动(B-29)
- Cargo.lock+Cargo.toml 依赖同步

crates/df-workflow/src/dag_def.rs

@@ -3,8 +3,6 @@
 use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 
-use crate::dag::Dag;
-
 /// DAG 定义 — 可序列化/反序列化，用于持久化和模板
 #[derive(Serialize, Deserialize, Clone, Debug)]
 pub struct DagDef {
@@ -73,28 +71,6 @@ impl DagDef {
             condition: Some(condition.into()),
         });
     }
-
-    /// 从已有的运行时 Dag 提取定义（忽略节点实例，仅保留元数据）
-    ///
-    /// 注意：此方法只能提取边的定义，节点配置无法从 trait object 反推
-    pub fn from_dag_edges(dag: &Dag) -> Self {
-        let edges: Vec<EdgeDef> = dag.edges.iter().map(|e| EdgeDef {
-            source: e.source.clone(),
-            target: e.target.clone(),
-            condition: e.condition.clone(),
-        }).collect();
-
-        let nodes: HashMap<String, NodeDef> = dag.nodes.iter().map(|(id, node)| {
-            (id.clone(), NodeDef {
-                id: id.clone(),
-                node_type: node.node_type().to_string(),
-                config: serde_json::Value::Null,
-                label: None,
-            })
-        }).collect();
-
-        Self { nodes, edges }
-    }
 }
 
 impl Default for DagDef {