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>

.github/templates/codex-plugin.json.tmpl

@@ -0,0 +1,36 @@
+{
+  "name": "{{PLUGIN_NAME}}",
+  "version": "{{VERSION}}",
+  "description": "Полный цикл разработки на платформе 1С:Предприятие 8.3 — от создания конфигураций, расширений, внешних обработок и отчётов до загрузки изменений в информационную базу, обновления, запуска, публикации на веб-сервере, тестирования через веб-клиент и записи видеоинструкций.",
+  "author": {
+    "name": "Nikolay Shirokov"
+  },
+  "homepage": "https://github.com/Nikolay-Shirokov/cc-1c-skills",
+  "repository": "https://github.com/Nikolay-Shirokov/cc-1c-skills",
+  "license": "MIT",
+  "keywords": [
+    "1c",
+    "1c-dev",
+    "cf",
+    "cfe",
+    "epf",
+    "erf",
+    "metadata",
+    "configuration",
+    "extension",
+    "form",
+    "report",
+    "skd",
+    "data-processor",
+    "mxl",
+    "web-client",
+    "testing",
+    "test-automation"
+  ],
+  "skills": "./.codex/skills/",
+  "interface": {
+    "displayName": "1C Skills ({{RUNTIME_LABEL}})",
+    "shortDescription": "{{SHORT_DESCRIPTION}}",
+    "category": "Development"
+  }
+}