修正文档中的像素规整与外部 API 契约

同步角色与图片画布文档的 Lanczos、去背和像素规整执行顺序
补全外部 OpenAPI 四个稳定 warning code 的语义
为外部编辑器 skill 补充顶层 style 参数、兼容规则和请求示例

.codex/skills/genarrative-external-editor-api/SKILL.md

@@ -115,6 +115,8 @@ python3 .codex/skills/genarrative-external-editor-api/scripts/genarrative_extern
 
 ## Request Patterns
 
+For image and icon generation, the request-body top-level `style` field controls deterministic post-processing and is distinct from `generationInputs.artSpec.style`, which describes visual style for prompting. Pass `style="pixelArt"` in Python or `"style": "pixelArt"` in JSON to enable pixel-art snapping on supported generation types; use `"none"` or omit the field otherwise. Verify compatibility and fallback semantics in `references/api-selection.md`.
+
 For Python callers, prefer:
 
 ```python

.codex/skills/genarrative-external-editor-api/references/api-selection.md

@@ -67,15 +67,44 @@ Ask a follow-up only when two routes could both be correct and produce different
 
 | User intent | Endpoint | Required fields | Common optional fields |
 | --- | --- | --- | --- |
-| Generate image/spec/character/UI/publication material | `POST /api/external/v1/editor/images/generations` | `prompt` | `kind`, `model`, `aspectRatio`, `imageSize`, `size`, `referenceImageSrcs`, `projectId`, `assetFolderId`, `assetLabel`, `canvasCompletion`, `generationInputs` |
+| Generate image/spec/character/UI/publication material | `POST /api/external/v1/editor/images/generations` | `prompt` | `kind`, `style`, `model`, `aspectRatio`, `imageSize`, `size`, `referenceImageSrcs`, `projectId`, `assetFolderId`, `assetLabel`, `canvasCompletion`, `generationInputs` |
 | Edit/redraw image | `POST /api/external/v1/editor/images/edits` | `prompt`, `sourceImageSrc` | `referenceImageSrcs`, `model`, `size`, `projectId`, `assetFolderId`, `assetLabel`, `sourceResourceId`, `targetLayerId`, `canvasCompletion` |
-| Generate icon spritesheet | `POST /api/external/v1/editor/icon-spritesheets/generations` | `referenceImageSrc`, `iconDescriptions` | `referenceImageSrcs`, `model`, `aspectRatio`, `imageSize`, `projectId`, `assetFolderId`, `canvasCompletion` |
+| Generate icon spritesheet | `POST /api/external/v1/editor/icon-spritesheets/generations` | `referenceImageSrc`, `iconDescriptions` | `style`, `referenceImageSrcs`, `model`, `aspectRatio`, `imageSize`, `projectId`, `assetFolderId`, `canvasCompletion` |
 | Extract assets from UI design | `POST /api/external/v1/editor/ui-designs/assets/extractions` | `sourceImageSrc`, `aspectRatio`, `imageSize` | `model`, `referenceImageSrcs`, `projectId`, `assetFolderId`, `spritesheetLabel`, `canvasCompletion` |
 | Generate character animation | `POST /api/external/v1/editor/character-animations/generations` | `sourceLayerId`, `sourceImageSrc`, `sourceWidth`, `sourceHeight`, `promptText`, `resolution`, `ratio`, `frameCount`, `durationSeconds`, `model` | `projectId`, `sourceResourceId`, `canvasCompletion`; then create a library asset from the first returned frame |
 | Generate video | `POST /api/external/v1/editor/videos/generations` | `prompt`, `model`, `aspectRatio`, `durationSeconds`, `resolution`, `mode`, `sound` | `referenceImageSrcs`, `referenceVideoSrcs`, `referenceAudioSrcs`, `webSearchEnabled`, `projectId`, `assetFolderId`, `assetLabel`, `canvasCompletion` |
 | Generate sound effect | `POST /api/external/v1/editor/audios/sound-effects/generations` | `prompt`, `duration` | `model`, `projectId`, `assetFolderId`, `assetLabel`, `canvasCompletion`, `generationInputs` |
 | Generate background music | `POST /api/external/v1/editor/audios/background-music/generations` | `gptDescriptionPrompt`, `makeInstrumental` | `projectId`, `assetFolderId`, `assetLabel`, `canvasCompletion`, `generationInputs` |
 
+## Image Post-processing Style
+
+The request-body top-level `style` field controls deterministic image post-processing. It is separate from `generationInputs.artSpec.style`, which only describes the requested visual language for prompting.
+
+- Omitted, `null`, an empty string, and `"none"` all disable post-processing without a warning.
+- `"pixelArt"` enables deterministic pixel-art snapping for ordinary image generation (omit `kind`), `kind: "character"`, and icon spritesheet generation.
+- Unknown strings, or `"pixelArt"` on unsupported image kinds such as `spec`, `quick-edit`, `ui-design`, or `publication-material`, continue without style processing and return `warning.code: "unsupported-image-style"`.
+- A non-string JSON value is malformed and returns HTTP `400`. Keep the field extensible; do not treat the current examples as a closed client-side enum.
+
+Image or character generation with pixel-art snapping:
+
+```json
+{
+  "prompt": "生成一个正面站立的像素风冒险者角色",
+  "kind": "character",
+  "style": "pixelArt"
+}
+```
+
+Icon spritesheet generation with pixel-art snapping:
+
+```json
+{
+  "referenceImageSrc": "generated-character-drafts/editor/external-editor-references/icon-spec.png",
+  "iconDescriptions": ["木剑", "圆盾", "红色药水"],
+  "style": "pixelArt"
+}
+```
+
 All generation requests should be placed into both the current canvas and its same-name asset-library folder. For endpoints that support `assetLabel`, pass it. For UI extraction, use `spritesheetLabel`. For icon spritesheet, the folder is enough. For character animation, the endpoint does not return `asset`; after success call `POST /api/external/v1/editor/assets` using the first returned frame as `imageSrc`, the session `assetFolderId`, and `assetKind: "character-animation"`.
 
 ## HTTP 2xx Warning Handling