refactor: move bundled skills tree to repo root skills/

- Relocate runtime/skills -> skills/; runtime_skills_root() prefers oclaw/skills
  with fallback to legacy runtime/skills for unmigrated trees.
- session-bootstrap hook handler resolves repo root via PROJECT_ROOT.
- Update architecture/migration docs and in-tree skill references.

Co-authored-by: Cursor <cursoragent@cursor.com>

skills/self-improvement/hooks/runtime/HOOK.md

@@ -0,0 +1,23 @@
+---
+name: self-improvement
+description: "在智能体启动阶段注入自我改进提醒"
+metadata: {"oclaw":{"emoji":"🧠","events":["agent:bootstrap"]}}
+---
+
+# 自我改进 Hook
+
+在 `agent:bootstrap` 阶段注入“学习沉淀提醒”。
+
+## 功能说明
+
+- 在 `agent:bootstrap` 触发（工作区文件注入前）
+- 注入提醒块，引导将学习写入 Wiki 路径
+- 提示智能体记录纠错、错误与新发现
+
+## 配置方式
+
+无需额外配置，启用命令：
+
+```bash
+oclaw hooks enable self-improvement
+```