docs(baoyu-article-illustrator,baoyu-comic,baoyu-infographic,baoyu-slide-deck,baoyu-xhs-images): point codex-imagegen flow at baoyu-image-gen --provider codex-cli

Add a `Codex via codex exec` branch to each skill's backend-selection
ladder and ship a per-skill references/codex-imagegen.md with the
invocation contract (preferred baoyu-image-gen --provider codex-cli
path, direct-wrapper fallback, parameter notes, stdout schema, batch
semantics).

skills/baoyu-xhs-images/SKILL.md

@@ -1,7 +1,7 @@
 ---
 name: baoyu-xhs-images
 description: Generates infographic image card series with 12 visual styles, 8 layouts, and 3 color palettes. Breaks content into 1-10 cartoon-style image cards optimized for social media engagement. Use when user mentions "小红书图片", "小红书种草", "小绿书", "微信图文", "微信贴图", "image cards", "图片卡片", baoyu-xhs-images, or wants social media infographic series.
-version: 2.0.0
+version: 2.0.1
 metadata:
   openclaw:
     homepage: https://github.com/JimLiu/baoyu-skills#baoyu-xhs-images
@@ -29,6 +29,7 @@ When this skill needs to render an image, resolve the backend in this order:
 2. **Saved preference** — if `EXTEND.md` sets `preferred_image_backend` to a backend available right now, use it.
 3. **Auto-select** (when the preference is `auto`, unset, or the pinned backend isn't available):
    - **Codex (`imagegen`)** — first, inspect your available-skills / tool inventory. If a skill named `imagegen` is listed, you are running inside Codex and MUST use it: invoke via the `Skill` tool with `skill: "imagegen"`, passing the saved prompt file's content (plus output path and aspect ratio per Codex `imagegen`'s own args). Codex `imagegen` is the official raster backend in that runtime and outranks any non-native skill (e.g., `baoyu-image-gen`) unless the user has explicitly pinned a different `preferred_image_backend`.
+   - **Codex via `codex exec` (`codex-imagegen`)** — if the current runtime exposes no native `imagegen` skill but the `codex` CLI is on `PATH` with an active `codex login`, route through `baoyu-image-gen --provider codex-cli` (preferred), or — if baoyu-image-gen is unavailable — invoke the bundled wrapper directly. Details, parameters, and the runtime-discovery procedure live in [references/codex-imagegen.md](references/codex-imagegen.md) — load that file only when this branch is selected.
    - **Other runtime-native tools** — if the runtime exposes a different native image tool (e.g., Hermes `image_generate`), use it the same way.
    - Otherwise, if exactly one non-native backend is installed (e.g., `baoyu-image-gen`), use it.
    - Otherwise (multiple non-native backends with no runtime-native tool), ask the user once — batch with any other initial questions.
@@ -387,6 +388,8 @@ See `references/config/watermark-guide.md`.
 
 **Backend selection**: per the Image Generation Tools rule at the top — use whatever is available, ask once if multiple, before any generation. Under `--yes`, use the EXTEND.md preference and fall back to the first available backend. Prompt files MUST exist before invoking any backend.
 
+**`codex-imagegen` invocation**: when the rule resolves to `codex-imagegen`, see [references/codex-imagegen.md](references/codex-imagegen.md) for the invocation contract (preferred `baoyu-image-gen --provider codex-cli` path, runtime wrapper discovery, parameter notes, stdout schema, batch semantics — n=1 per call so card batches must dispatch one wrapper call per card; the wrapper does NOT accept `--sessionId`, so chain consistency must come from `--ref` per Step 3 above).
+
 **Session ID** (if the backend supports `--sessionId`): use `cards-{topic-slug}-{timestamp}` for every image; combined with the ref chain this gives maximum consistency.
 
 ### Step 4: Completion Report