fix(codex): reject web_search for Qwen3-Coder and correct LongCat context window

- Add `qwen3-coder` to the web_search reject model-prefix blacklist so the
  native qwen3-coder-plus direct-connect preset suppresses the built-in tool
  (百炼 rejects it for the coder series), while general Qwen models sharing the
  DashScope host keep web_search enabled. Matched on the model axis, not host.
- Correct LongCat-2.0-Preview context window from 128K to its real 1M
  (1048576), aligning with the MiMo/Qwen 2^20 convention.
- Tighten native Responses preset tests to assert exact model→contextWindow
  catalogs instead of only checking catalog presence.

src/config/codexProviderPresets.ts

@@ -625,7 +625,7 @@ requires_openai_auth = true`,
       {
         model: "LongCat-2.0-Preview",
         displayName: "LongCat 2.0 Preview",
-        contextWindow: 131072,
+        contextWindow: 1048576,
       },
     ]),
     category: "cn_official",