feat(ui-models)!: single-key hand-written provider editors with derived credential references

The Models page drops the generic schema renderer and the visible
environment-variable field: each editor is a curated per-family card whose
primary input is one write-only API key stored under a derived
<ROUTE>_API_KEY reference (recorded as apiKeyEnv in the pi-ai profile), an
unkeyed whole-section provider opens as its setup card, and the collapsed
customized-settings fold carries baseURL/reasoningEffort (deepseek) or
reasoning (pi-ai). dsh-client-schema-form reduces to the schema/draft model
layer (no React).

apps/web/tests/snapshots/models-settings/empty.expected.md

@@ -13,8 +13,8 @@
   - heading "模型" [level=2]
   - paragraph: 填入各提供方的 API 密钥即可使用其模型。
   - list
-  - combobox "添加提供方":
-    - option "+ 添加提供方" [selected]
+  - text: 提供方
+  - combobox "提供方":
     - option "amazon-bedrock"
     - option "ant-ling"
     - option "anthropic"
@@ -31,7 +31,7 @@
     - option "huggingface"
     - option "kimi-coding"
     - option "minimax"
-    - option "minimax-cn"
+    - option "minimax-cn" [selected]
     - option "mistral"
     - option "moonshotai"
     - option "moonshotai-cn"
@@ -52,3 +52,9 @@
     - option "xiaomi-token-plan-sgp"
     - option "zai"
     - option "zai-coding-cn"
+  - text: API 密钥
+  - textbox "API 密钥":
+    - /placeholder: 输入 API 密钥
+  - group: 自定义设置
+  - button "取消"
+  - button "保存"