fix: allow deleting system default sync channel with immediate heal

Remove hard ban that returned 400 with no UI feedback; delete then Ensure+rebinding, and show confirm/toast on SyncPage.

Co-authored-by: Cursor <cursoragent@cursor.com>

platform/internal/handler/sync.go

@@ -121,21 +121,23 @@ func syncDeleteHandler(svcCtx *svc.ServiceContext) http.HandlerFunc {
 			authx.WriteError(w, http.StatusNotFound, err.Error())
 			return
 		}
-		// Z12h-1：公司默认同步通道禁止删除（账号落点依赖它）
-		if ch.IsSystemDefault {
-			authx.WriteError(w, http.StatusBadRequest, "公司默认同步通道不可删除；账号绑定落点依赖此通道。若异常请刷新页面自动修复")
-			return
-		}
+		wasDefault := ch.IsSystemDefault
 		svcCtx.DBSync.StopChannel(id)
 		if err := svcCtx.DBSync.Store().DeleteChannel(id); err != nil {
 			authx.WriteError(w, http.StatusBadRequest, err.Error())
 			return
 		}
-		// 若误删后仍有 Binding 挂死，heal 会挂回默认通道
-		if _, hErr := applogic.HealTenantSyncBind(r.Context(), svcCtx, tid); hErr != nil {
-			_ = hErr
+		// Z12h-1：默认同步可删；删后 Ensure+heal，账号落点自动挂回新默认通道
+		out := map[string]any{"ok": true, "deleted_id": id, "was_system_default": wasDefault}
+		if healed, hErr := applogic.HealTenantSyncBind(r.Context(), svcCtx, tid); hErr != nil {
+			out["heal_error"] = hErr.Error()
+		} else if healed != nil {
+			out["channel_id"] = healed.ChannelID
+			out["recreated_default"] = wasDefault || healed.ChannelCreated
+			out["bindings_fixed"] = healed.BindingsFixed
+			out["agents_fixed"] = healed.AgentsFixed
 		}
-		httpx.OkJson(w, map[string]any{"ok": true})
+		httpx.OkJson(w, out)
 	}
 }