fix(audit): Batch 0-1 文档校准 + let _ = 静默错误修复

Batch 0:
- TRUTH.md 中间件层 14→15 (补 EvolutionMiddleware@78)
- wiki/middleware.md 同步 15 层 + 优先级分类更新
- Store 数字确认 25 个

Batch 1:
- approvals.rs: 3 处 map_err+let _ = 简化为 if let Err
- director.rs: oneshot send 失败添加 debug 日志
- task.rs: 4 处子任务状态更新添加 debug 日志
- chat.rs: 流消息发送和事件 emit 添加 warn/debug 日志
- heartbeat.rs: 告警广播添加 debug 日志 + break 优化

全量测试通过: 719 passed, 0 failed

crates/zclaw-kernel/src/director.rs

@@ -573,10 +573,13 @@ Respond with ONLY the number (1-{}) of the agent who should speak next. No expla
                     // Find and dispatch to the correct oneshot sender
                     if msg.message_type == A2aMessageType::Response {
                         if let Some(ref reply_to) = msg.reply_to {
+                            let reply_to_clone = reply_to.clone();
                             let mut pending_guard = pending.lock().await;
                             if let Some(sender) = pending_guard.remove(reply_to) {
-                                // Send the response; if receiver already dropped, that's fine
-                                let _ = sender.send(msg);
+                                // Send the response; if receiver already dropped, request was cancelled
+                                if sender.send(msg).is_err() {
+                                    tracing::debug!("[Director] Response dropped: receiver cancelled for reply_to={}", reply_to_clone);
+                                }
                             }
                         }
                     }