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/README.md

@@ -0,0 +1,14 @@
+# self-improvement
+
+Self-improvement skill for Oclaw. It captures learnings, errors, and feature requests to support continuous improvement across sessions.
+
+## Attribution
+
+Remade for Oclaw from the original repo:
+
+- https://github.com/pskoett/pskoett-ai-skills
+- https://github.com/pskoett/pskoett-ai-skills/tree/main/skills/self-improvement
+
+## Main File
+
+- `SKILL.md`