feat(skills): enhance skills system with matching and evaluation

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/app/agents/skills/effectiveness.py

@@ -0,0 +1,14 @@
+from __future__ import annotations
+
+from app.models.skill import Skill
+
+
+def summarize_skill_effectiveness(skill: Skill) -> dict[str, object]:
+    return {
+        "name": skill.name,
+        "status": skill.status,
+        "effectiveness": skill.effectiveness,
+        "activation_count": skill.activation_count,
+        "candidate_count": getattr(skill, "candidate_count", 0),
+        "last_activated_at": skill.last_activated_at.isoformat() if skill.last_activated_at else None,
+    }