v0.0.100 - Remove GPT5-Codex (#533)

🌟 Summary

v0.0.100 switches Ultralytics Actions over to the dated gpt-5-2025-08-07 model and refreshes CI tooling so automation stays accurate and future-proof. 🤖🚀

📊 Key Changes

• 🧠 Swapped the default OpenAI model from gpt-5-codex to gpt-5-2025-08-07 in action.yml and OPENAI_MODEL fallback logic.
• 🔢 Bumped the Ultralytics Actions package version to 0.0.100.
• 🛠️ Upgraded all workflows to actions/setup-python@v6, aligning with the latest GitHub Actions runtime requirements.

🎯 Purpose & Impact

• ✅ Restores the high-performing GPT5 model lineage so automated summaries stay sharp and reliable.
• 📦 Version bump clearly marks the release for anyone pinning or auditing Ultralytics Actions.
• ⚙️ Modern CI tooling improves compatibility with new runners (requires GitHub Actions runner v2.327.1 or newer) and unlocks future Python setup enhancements for contributors.

What's Changed

• Revert "Update to GPT5-Codex model" by @glenn-jocher in #530
• Bump actions/setup-python from 5 to 6 by @dependabot[bot] in #532
• Bump actions/setup-python from 5 to 6 in /.github/workflows by @dependabot[bot] in #531
• Remove GPT5-Codex by @glenn-jocher in #533

Full Changelog: v0.0.99...v0.0.100