catalog: add DeepSeek Harness Handbook

[denial123789]

Summary

• adds the DeepSeek Harness Handbook to Essential Readings & Ecosystem Maps
• renders the English and Chinese catalogs from the source data
• removes the AGENT.md entry, whose repository has been inactive for more than 12 months and now fails the catalog's activity policy
• includes the 2026-08-14 verification report

Why it fits

The handbook is a practical companion to the existing official DeepSeek Harness runtime entry. It covers runtime composition, durable sessions, tools and policy, sandbox boundaries, MCP, headless CI, Windows limitations, and failure diagnosis, with official source links and verification dates.

Verification

python3 scripts/render_readme.py
python3 scripts/verify_catalog.py --skip-links
Verification passed.