docs: add installation validation workflow

SKILL.md

@@ -11,7 +11,7 @@ Use this helper when image generation or editing should reach server6 directly i
 
 - Do not print, copy, commit, or summarize API keys.
 - Read only `OPENAI_API_KEY` from `~/.codex/auth.json`; do not read plaintext `.env` files or unrelated secrets.
-- Keep the durable source at `ai-infra/skills/sources/shujkimagegen-api/`.
+- Keep the durable source in the Gitea repo `shujakuin/skill-shujkimagegen-api`; treat `ai-infra/skills/sources/shujkimagegen-api/` and HOME runtime copies as managed mirrors.
 - Do not place this skill under the infra repo's `.agents/skills/` or manage it through cc-switch WebDAV.
 - Treat this as a thin wrapper around the system `imagegen` CLI; do not copy or patch the system script.
 - The current management state is repo source only. Do not create a HOME runtime placement unless the user explicitly requests it.
@@ -54,6 +54,31 @@ The `/v1` suffix is required because `/models` is an application page while `/v1
 
 After an explicit HOME runtime placement, use the equivalent path under `~/.agents/skills/shujkimagegen-api/`.
 
+## Installation Validation
+
+After placing the skill in `~/.agents/skills/shujkimagegen-api/`, validate the installed copy before reporting success:
+
+1. Confirm `SKILL.md`, `agents/openai.yaml`, and `scripts/shujk_imagegen.py` exist.
+2. Check whether the selected Python environment can import `openai`. Do not add it to an unrelated project's dependencies just for validation. If it is absent and `uv` is available, use an ephemeral environment:
+
+   ```bash
+   uv run --with openai python ~/.agents/skills/shujkimagegen-api/scripts/shujk_imagegen.py \
+     --print-config-redacted
+   ```
+
+3. Run a no-cost command-path test:
+
+   ```bash
+   uv run --with openai python ~/.agents/skills/shujkimagegen-api/scripts/shujk_imagegen.py \
+     generate --prompt "installation validation" --out /tmp/shujkimagegen-dry-run.png \
+     --dry-run --no-augment
+   ```
+
+4. When the user authorizes a real API test, generate one low-cost image with `gpt-image-2`, `quality=low`, and a simple prompt. Confirm the command exits successfully and inspect the resulting file as a real, non-empty image.
+5. Remove test artifacts that are not intended deliverables.
+
+If validation requires a compatibility fix, edit the standalone Gitea checkout first, rerun validation, commit and push it, then resync the infra mirror and selected runtime placement. Never leave the only fix in `~/.agents/skills/`.
+
 ## Failure Handling
 
 - If `OPENAI_API_KEY` is absent, report that auth is unavailable without revealing file contents.