AGENTS.md (546 -> 63 lines) now carries only project-global development
rules: hard constraints, mount-smoke CI, DSH 0.1.2-alpha.1 adaptation
notes, npm release, a quick-rule list, and a docs/tests map. The
consumer plugin API reference lives solely in
docs/external-plugin-guide.md.
Reference sync:
- README/README_EN: collapse the dual 'full integration docs' links to
the guide; AGENTS.md stays linked as the repo rules
- shell-presets.ts / mount.e2e.ts comments: skinning contract pointer
moved from AGENTS.md §8 to guide §12