feat: support GPT Image 2.5 request parameters

[ningzimu]

Summary

• Default image requests to GPT Image 2.5 Flare and allow Sunburst selection.
• Support xhigh/max quality and transparent PNG/WebP with model-specific validation.
• Distinguish requested models from backend-reported models and document OAuth limitations.

User-visible changes

• Add GPT Image 2.5 options while preserving legacy model validation.
• Update Chinese and English usage documentation and the skill reference.

Changelog

• Updated CHANGELOG.md

Verification

• python3 -m unittest discover -s tests -v: 6 tests passed.
• python3 -m py_compile skills/codex-gpt-image/scripts/codex_gpt_image.py: passed.
• git diff --check: passed.
• Live Codex OAuth requests returned images for both model names, a transparent PNG with alpha, and a blue-to-green cup edit.

Notes

An invalid model name also returned an image. The backend omitted the actual model ID and returned dimensions different from the requested size. Successful requests therefore do not establish actual model routing or quality enforcement. Generated test images are excluded from this PR.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-10T17:36:59.681413Z	1e3a647	PR opened

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