fix(web): edit a declared provider's name and protocol

The Models editor card curated its pi-ai fields by what every route has,
so `displayName` and `api` — the two a hand-declared route names for
itself — were asked for at creation and then reachable only through
settings.yaml. The editor now renders both for a route the directory
reports as declared, from the same namespace schema the create card
reads. A catalog route gets neither: it defaults its name from its
catalog entry, and its models each carry their own protocol, so a
route-level one could only override all of them.

Clearing the name unsets it and the route falls back to its id, which is
what the field's placeholder shows; storing the empty string would be
refused by the adapter. A declared profile naming no protocol selects
nothing rather than reading as if it had picked the first choice.

The Provider ID stays fixed: it is the settings dict key, it is
referenced from `agent-default-model` and every logged request header,
and it is the stem of a credential reference the page can never read
back to move.

Fixes #2204

docs/user/guide/providers.zh.md

@@ -29,6 +29,8 @@ Harness 出厂自带 DeepSeek，同时预装了一个通用的多提供方适配
 
 ![自定义提供方表单：Provider ID、显示名称、API 地址、API 协议、API 密钥](providers-custom-form.zh.png)
 
+除 Provider ID 外的每个字段之后都还能改：行上的**编辑**会重新打开这些字段，显示名称和协议在「自定义设置」里、紧挨着 API 地址；显示名称清空即退回 Provider ID。Provider ID 本身固定不可改：它在请求里、在 `agent-default-model` 里、在每一条已记录的会话里点名这条路由，同时还是凭据引用的词干，而页面永远读不回凭据值——因此重命名一条路由等于声明一个新提供方再把旧的删掉。
+
 **让端点自己报模型。** 展开**模型目录**后点**获取可用模型**，会按你**当前表单里**的地址与密钥去问端点（地址改了但没保存、密钥刚输入还没存下，都算数），把它报告的模型列成候选让你勾选。内置目录里的路由直接由目录作答，不联网。采纳只是把行写进草稿，最终还是你点保存才落盘。
 
 密钥是只写的：页面拿到的永远是脱敏描述符，不是明文。写入的密钥存进 `$DSH_HOME/.credentials.yaml`，profile 里只记录引用它的变量名。