feat(codex-image): 封装 GPT Image 2 图片接口并收紧错误处理

- 新增 openai:image 路由、planner 与 finalize，内部通过 Codex responses image_generation tool 执行生图

- 补充 Codex OAuth/header 兼容、图片 success report 本地处理与相关前后端/集成测试

- 禁止 chat/completions 使用 gpt-image-2，图片接口限制 n=1，并移除 Provider 模型页的图片能力开关

apps/aether-gateway/src/tests/architecture/ai_pipeline.rs

@@ -480,6 +480,7 @@ fn ai_pipeline_candidate_preparation_owns_shared_auth_and_mapped_model_resolutio
     for path in [
         "apps/aether-gateway/src/ai_pipeline/planner/standard/openai/chat/decision/request.rs",
         "apps/aether-gateway/src/ai_pipeline/planner/standard/openai/cli/decision/request.rs",
+        "apps/aether-gateway/src/ai_pipeline/planner/specialized/image/request.rs",
         "apps/aether-gateway/src/ai_pipeline/planner/standard/family/request.rs",
     ] {
         let source = read_workspace_file(path);