release: 0.2.1 (#204)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

changelog/0.2.1/2026-08-04-skill-porting-library-skill.md

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+# Skills: skill-porting — install skills from any ecosystem
+
+New library skill `skill-porting` (agent-tuning group) teaching an agent to bring skills in from the outside world and land them correctly in `agent_state/skills/<name>/`. Its schema tables were verified by directly fetching each source on 2026-08-04 — the skill says so and treats the live JSON as authoritative:
+
+- **Claude Code plugin marketplaces** (`anthropics/claude-plugins-official`, 278 plugins): the marketplace.json shape, all four `source` forms (relative path, sha-pinned `url`, `git-subdir`, `github`) and the five places a plugin can keep skills.
+- **Codex plugins** (`openai/plugins`, 180 plugins): the `.agents/plugins/marketplace.json` entry shape with its `policy` block and `.codex-plugin/plugin.json` layout.
+- **`npx skills add` / skills.sh** (`vercel-labs/skills`): spec forms, per-agent install destinations, and the in-repo discovery order — resolved by fetching from the source repo, never by blindly running the installer.
+- Plain **GitHub repos/subdirectories** (sparse checkout / tarball / raw fetch variants) and **local folders**, plus the agentskills.io SKILL.md convention.
+
+Each flow ends in the same normalization: adapt frontmatter to penguin's fields (`short_description`, `short_description_zh`, integer `version`, `updated`), port or drop commands/agents/hooks penguin has no runtime for (honestly — the skill forbids pretending a dropped capability survived), and verify the install. Safety first is mandatory: read every file before installing, refuse content that exfiltrates, phones home, or overrides safety rules, prefer pinned revisions.
+
+The web Import dialog's generated prompt points agents at this skill when it is installed. Docs skill tables (en/zh) gained the one row the library-sync test requires.