docs: remove the roadmap and bring the docs in line with the current code [SKIP TESTS]

Probes link to the panel directly, container nodes update through signed
releases, the frontend exists and the ports changed. The roadmap is gone; its
open items live in the README.

docs/fleet/overview.md

@@ -1,5 +1,7 @@
 # Fleet：通用节点框架
 
+> **实现状态**：`Fleet.Update`、`Fleet.Server.Releases`、`fleet-updater`、`fleet-release` 还只是设计；容器节点的更新目前由宿主机上的 `monitor-update` 脚本和 Monitor 的 `ReleaseService` 完成（见 [deployment.md](../deployment.md)）。其余组件已实现。
+
 > 名称暂定。Fleet 与业务无关，Monitor 是它的第一个使用者。
 
 ## 1. 定位