feat(codex): add DeepSeek native Responses support with official catalog mirror

- Switch the DeepSeek preset to openai_responses and align context
  windows with the official catalog (1048576)
- Mirror DeepSeek's official models.json verbatim for native /responses
  providers on deepseek.com hosts, keeping the official GPT-5 harness
  and freeform apply_patch registration self-consistent
- Make catalog spec displayName/contextWindow explicit-only (Option) so
  local defaults no longer clobber official vendor values

tests/config/codexChatProviderPresets.test.ts

@@ -24,16 +24,6 @@ const expectedChatPresets = new Map<
       contextWindows: { "ark-code-latest": 256000 },
     },
   ],
-  [
-    "DeepSeek",
-    {
-      baseUrl: "https://api.deepseek.com",
-      contextWindows: {
-        "deepseek-v4-flash": 1000000,
-        "deepseek-v4-pro": 1000000,
-      },
-    },
-  ],
   [
     "Zhipu GLM",
     {
@@ -171,6 +161,17 @@ describe("Codex Chat provider presets", () => {
         { contextWindows: { "doubao-seed-2-1-pro-260628": 262144 } },
       ],
       ["Bailian", { contextWindows: { "qwen3-coder-plus": 1048576 } }],
+      // DeepSeek 官方 Codex 文档确认 deepseek-v4-flash 原生 Responses；
+      // catalog 由后端按 deepseek.com host 镜像官方 models.json 生成
+      [
+        "DeepSeek",
+        {
+          contextWindows: {
+            "deepseek-v4-flash": 1048576,
+            "deepseek-v4-pro": 1048576,
+          },
+        },
+      ],
       ["Longcat", { contextWindows: { "LongCat-2.0": 1048576 } }],
       ["MiniMax", { contextWindows: { "MiniMax-M3": 1000000 } }],
       ["MiniMax en", { contextWindows: { "MiniMax-M3": 1000000 } }],