feat: add OpenAI Agents API operations post

[moony01]

Summary

• Add a Korean post about the operational boundaries of OpenAI Agents API.
• Cover managed Codex harness, sessions, sandbox isolation, compaction, MCP/tools, approvals, and a bounded adoption checklist.
• Add two newly generated 16:9 PNG illustrations.

Verification

• Citation ledger verification: PASS
• git diff --check: PASS
• CI-equivalent Node 20 + Ruby/Jekyll build: PASS
• Local browser smoke: PASS
  • Article route rendered with title and body
  • Hero and body WebP images returned HTTP 200
  • Both lazy-loaded images decoded at 1672px natural width

Deployment

After required PR checks pass, merge to main and verify the GitHub Pages production URL:

https://moony01.com/ai/2026/09/24/openai-agents-api-ops.html