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

src-tauri/src/commands/mod.rs

@@ -12,10 +12,8 @@ pub mod task;
 pub mod workflow;
 
 /// 当前时间戳（毫秒字符串）— 与 df-storage 内部的时间格式保持一致
+///
+/// 转发 df_core::now_millis(DRY:时间获取统一入口在此 crate,避免 commands 层与 df-storage 各写一份 SystemTime 调用)。
 pub(crate) fn now_millis() -> String {
-    std::time::SystemTime::now()
-        .duration_since(std::time::UNIX_EPOCH)
-        .unwrap_or_default()
-        .as_millis()
-        .to_string()
+    df_core::now_millis().to_string()
 }