feat(plugins): Codex plugin support + Python plugin variant for Claude

- Add 1c-skills-py to .claude-plugin/marketplace.json (→ port-claude-code-py)
- New .agents/plugins/marketplace.json — Codex marketplace with PS + Py plugins
- Templates .github/templates/{codex,claude}-plugin.json.tmpl rendered by CI
- build-ports.yml: generate plugin manifests on port-codex/port-codex-py/port-claude-code-py; Codex version YYYY.M.D+sha7 auto-bumped per push
- README: install instructions for Codex + Py variant for Claude
- .gitignore: narrow .agents/ → .agents/skills/ so the marketplace is tracked

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -37,7 +37,7 @@ __pycache__/
 *.mp4
 
 # Навыки, скопированные для других AI-платформ (генерируются scripts/switch.py)
-.agents/
+.agents/skills/
 .augment/
 .cline/
 .codex/