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-article-illustrator/SKILL.md

@@ -1,7 +1,7 @@
 ---
 name: baoyu-article-illustrator
 description: Analyzes article structure, identifies positions requiring visual aids, generates illustrations with Type × Style × Palette three-dimension approach. Use when user asks to "illustrate article", "add images", "generate images for article", or "为文章配图".
-version: 1.117.3
+version: 1.117.4
 metadata:
   openclaw:
     homepage: https://github.com/JimLiu/baoyu-skills#baoyu-article-illustrator
@@ -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.
@@ -185,6 +186,7 @@ Full template: [references/workflow.md](references/workflow.md#step-4-generate-o
 4. LABELS **MUST** include article-specific data: actual numbers, terms, metrics, quotes
 5. **DO NOT** pass ad-hoc inline prompts to `--prompt` without saving prompt files first
 6. Select the backend via the `## Image Generation Tools` rule at the top: use whatever is available; if multiple, ask the user once. Do this once per session before any generation.
+   - **`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).
 7. **Execution strategy**: Generate in batches per the `## Batch Generation Policy`: backend native batch first, runtime parallel tool calls second, sequential only as fallback. Default batch size is 4 unless EXTEND.md or the current request overrides it.
 8. Process references (`direct`/`style`/`palette`) per prompt frontmatter
 9. Apply watermark if EXTEND.md enabled