feat(memory): add memory backup directory

HERMES_MEMORY.md / HERMES_USER.md snapshots of ~/.hermes/memories/
同步方法见 memory/README.md
备份 ~/.hermes/memories/{MEMORY,USER}.md 到这里方便追溯

Co-Authored-By: Claude <noreply@anthropic.com>

memory/README.md

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+# Hermes Memory Backup
+
+手动同步备份 `~/.hermes/memories/`(MEMORY.md + USER.md)到 git,方便追溯。
+
+## 同步方法
+```bash
+# 备份最新 memory 到这里
+cp ~/.hermes/memories/MEMORY.md ~/.hermes/skills/trading/memory/HERMES_MEMORY.md
+cp ~/.hermes/memories/USER.md ~/.hermes/skills/trading/memory/HERMES_USER.md
+
+cd ~/.hermes/skills/trading
+git add memory/
+git commit -m "memory backup: <date>"
+git push origin master
+```
+
+## 为什么不直接 git 跟踪 ~/.hermes/memories
+- skills 仓库干净,不混入 Hermes 运行时文件
+- memory 含敏感信息(凭证模式、用户偏好),与 skills 分开 review 更安全
+- 避免 `~/.hermes/.git` 干扰 Hermes 其他目录