Remove connectonion-claude-plugin; install skills directly from openonion/oo bundle

[wu-changxing]

Problem

We currently maintain a separate repo, openonion/connectonion-claude-plugin, that ships the Linus/Aaron review skills, aaron-build-my-agent, generate-code-map-headers, and design-refine as a Claude Code plugin.

This duplicates effort with openonion/oo, which is already the canonical SKILL.md bundle and fans out to Claude / Codex / Cursor / Kiro / OpenClaw via a single source of truth (skills/<name>/SKILL.md).

Maintaining two plugin/marketplace surfaces (connectonion-claude-plugin and oo) means:

• Two places to update when a skill changes — drift is inevitable.
• Two install instructions for users — confusing onboarding.
• The connectonion-specific plugin only targets Claude Code; oo already covers all coding agents.

Proposal

1. Move the plugin's skills (linus-review-my-code, aaron-review-my-code, aaron-build-my-agent, generate-code-map-headers, design-refine) into openonion/oo under skills/<name>/SKILL.md.
2. Update docs and README.md to point users at openonion/oo for installation:

   curl -fsSL agent.openonion.ai/install | sh
   

   instead of /plugin marketplace add openonion/connectonion-claude-plugin.
3. Archive openonion/connectonion-claude-plugin (leave a redirect note in its README pointing to oo).
4. Verify each migrated skill still works in Claude Code, Codex, Cursor, Kiro, OpenClaw via oo's installer.

Why now

oo already established the "skill IS the interface" pattern; the standalone plugin is the last holdout. Folding it in lets us delete a repo, simplify the install story, and give the review/build skills cross-tool reach for free.

Out of scope

• No changes to the connectonion library itself.
• No changes to skill content — straight migration first, refinements after.