[docs] docs: tighten ARC DinD Copilot setup guide

[github-actions]

Overview

This PR reduces bloat in docs/src/content/docs/guides/arc-dind-copilot-agent.md while preserving the setup, troubleshooting, and version requirements.

What changed

• condensed the ARC DinD runtime behavior section from a long bullet list into direct prose
• collapsed repetitive "not required", migration, and rootless-install bullets into shorter explanatory text
• tightened the related documentation list wording without removing links

Impact

• improved file: docs/src/content/docs/guides/arc-dind-copilot-agent.md
• line reduction: 283 → 265 (~6%)
• bullet reduction: several repeated operational lists were consolidated into prose for faster scanning

Notes

All essential configuration details, warnings, troubleshooting entries, and code samples were preserved.

🗜️ Compressed by Documentation Unbloat · gpt54 13.2 AIC · ⌖ 12.2 AIC · ⊞ 6.4K · ◷
_{Comment /unbloat to run again}

• expires on Jul 24, 2026, 5:05 PM UTC-08:00