feat(codex): 新增 Codex CLI 插件市场支持，含独立 memcore-codex

huanxi/huanxi-admin/obsidian 复用 Claude Code 版技能内容，新增
.codex-plugin/plugin.json + .mcp.json（Token 走环境变量，Codex 无等价
钥匙链机制）。memcore 因架构差异（AGENTS.md 会话入口、.codex/memory
目录约定、无远程同步）独立新增 memcore-codex 插件：以本机已装的 Codex
原生版为底稿，抽出 memcore-shared 共享 include，并吸纳 Claude 版的速
度分档过期检测、NEED-HUMAN 稳定 ID 保活、兜底锚点、更完整报告模板四
项内容。新增 .agents/plugins/marketplace.json 收录四个插件，均通过
Codex 官方 validate_plugin.py 校验。

README/CHANGELOG 同步补充双端安装配置引导。删除已被取代的旧
feat/codex-marketplace 骨架分支和已合并的 feat/memcore-optimizations 分支。

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LVyxoP4cDXeoQ3uAqLcEd2

.agents/plugins/marketplace.json

@@ -0,0 +1,56 @@
+{
+  "name": "yixiong-codex-hub",
+  "interface": {
+    "displayName": "蚁熊 Codex 技能市场"
+  },
+  "plugins": [
+    {
+      "name": "huanxi",
+      "source": {
+        "source": "local",
+        "path": "./plugins/huanxi"
+      },
+      "policy": {
+        "installation": "AVAILABLE",
+        "authentication": "ON_INSTALL"
+      },
+      "category": "Productivity"
+    },
+    {
+      "name": "huanxi-admin",
+      "source": {
+        "source": "local",
+        "path": "./plugins/huanxi-admin"
+      },
+      "policy": {
+        "installation": "AVAILABLE",
+        "authentication": "ON_INSTALL"
+      },
+      "category": "Productivity"
+    },
+    {
+      "name": "memcore",
+      "source": {
+        "source": "local",
+        "path": "./plugins/memcore-codex"
+      },
+      "policy": {
+        "installation": "AVAILABLE",
+        "authentication": "ON_INSTALL"
+      },
+      "category": "Productivity"
+    },
+    {
+      "name": "obsidian",
+      "source": {
+        "source": "local",
+        "path": "./plugins/obsidian"
+      },
+      "policy": {
+        "installation": "AVAILABLE",
+        "authentication": "ON_INSTALL"
+      },
+      "category": "Productivity"
+    }
+  ]
+}