整体删除已退役的 gpt-image-2-c

- 删除 platform-image 的 GPT_IMAGE_2_C_MODEL 常量、re-export、尺寸语义与审计标签
- 移除 api-server 三处任务边界对 gpt-image-2-c 的兼容解析分支
- 移除主站前端历史模型常量与恢复分支，并同步其测试
- 同步 External v1 OpenAPI 描述、ADR、CONTEXT、pitfalls 与后端/运维文档
- 数据库既有 gpt-image-2-c 审计字符串保持原样，不回写不改写

src/components/image-editor/ImageCanvasGenerationModel.test.ts

@@ -49,7 +49,6 @@ import {
   getGenerationFrameLabel,
   IMAGE_MODEL_GPT_IMAGE_2,
   IMAGE_MODEL_GPT_IMAGE_2_5,
-  IMAGE_MODEL_GPT_IMAGE_2_C,
   IMAGE_MODEL_NANOBANANA2,
   isNormalizedCanvasGenerationInputs,
   isQuickEditSupportedLayer,
@@ -726,32 +725,6 @@ describe('ImageCanvasGenerationModel', () => {
     ).toBe(IMAGE_MODEL_NANOBANANA2);
   });
 
-  it('restores the concrete legacy GPT image value to GPT Image 2.5 with a warning', () => {
-    const decoded = decodeCanvasGenerationInputs({
-      version: 2,
-      action: 'image.generate',
-      fields: [
-        { id: 'prompt', title: '生成提示词', value: '旧模型素材' },
-        { id: 'model', title: '模型', value: IMAGE_MODEL_GPT_IMAGE_2_C },
-        { id: 'aspectRatio', title: '比例', value: '1:1' },
-        { id: 'imageSize', title: '尺寸', value: '1K' },
-      ],
-      references: [],
-    });
-
-    expect(decoded).toMatchObject({
-      ok: true,
-      inputs: {
-        fields: expect.arrayContaining([
-          { id: 'model', title: '模型', value: IMAGE_MODEL_GPT_IMAGE_2_5 },
-        ]),
-      },
-      warnings: expect.arrayContaining([
-        expect.objectContaining({ fieldIds: ['model'] }),
-      ]),
-    });
-  });
-
   it('falls invalid image and workflow parameters back within V2', () => {
     const image = decodeCanvasGenerationInputs({
       version: 2,

src/components/image-editor/ImageCanvasGenerationModel.ts

@@ -44,7 +44,6 @@ import {
 
 // 中文注释：与 api-server/src/editor_generation_config.rs 保持同名模型定价语义，前端仅作为展示兜底。
 export const IMAGE_MODEL_GPT_IMAGE_2 = 'gpt-image-2';
-export const IMAGE_MODEL_GPT_IMAGE_2_C = 'gpt-image-2-c';
 export const IMAGE_MODEL_GPT_IMAGE_2_5 = 'gpt-image-2.5';
 export const IMAGE_MODEL_NANOBANANA2 = 'gemini-3.1-flash-image-preview';
 export const DEFAULT_IMAGE_MODEL = IMAGE_MODEL_NANOBANANA2;
@@ -54,10 +53,7 @@ const IMAGE_MODEL_NANOBANANA_ALIASES = new Set([
   'nano-banana',
 ]);
 // 历史 GPT Image 2 别名统一映射到当前业务模型，判定与归一复用同一集合。
-const LEGACY_EDITOR_IMAGE_MODELS = new Set([
-  IMAGE_MODEL_GPT_IMAGE_2,
-  IMAGE_MODEL_GPT_IMAGE_2_C,
-]);
+const LEGACY_EDITOR_IMAGE_MODELS = new Set([IMAGE_MODEL_GPT_IMAGE_2]);
 export const SPEC_GENERATION_MODEL = IMAGE_MODEL_GPT_IMAGE_2_5;
 export const SPEC_GENERATION_ASPECT_RATIO = '16:9';
 export const SPEC_GENERATION_IMAGE_SIZE = '2K';