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/evaluator.py

@@ -0,0 +1,58 @@
+from __future__ import annotations
+
+from datetime import UTC, datetime, timedelta
+
+from app.agents.schemas.learning import SessionRetrospective, SkillCandidate
+from app.agents.skills.models import SkillLifecycleDecision
+from app.services.skill_service import SkillService
+
+
+class SkillPromotionEvaluator:
+    def __init__(self, db):
+        self.db = db
+        self.skill_service = SkillService(db)
+
+    async def sync_retrospective(
+        self,
+        *,
+        user_id: str,
+        retrospective: SessionRetrospective,
+    ) -> list[SkillLifecycleDecision]:
+        decisions: list[SkillLifecycleDecision] = []
+
+        for candidate in retrospective.skill_candidates:
+            decisions.append(
+                await self.skill_service.upsert_learned_candidate(
+                    user_id=user_id,
+                    candidate=candidate,
+                    primary_agent=retrospective.primary_agent,
+                    evidence_refs=candidate.evidence_refs,
+                )
+            )
+
+        outcome_score = self._derive_outcome_score(retrospective)
+        for skill_name in retrospective.used_skill_names:
+            decision = await self.skill_service.record_activation_feedback(
+                user_id=user_id,
+                skill_name=skill_name,
+                outcome_score=outcome_score,
+                evidence_refs=retrospective.evidence_refs,
+            )
+            if decision is not None:
+                decisions.append(decision)
+
+        return decisions
+
+    @staticmethod
+    def _derive_outcome_score(retrospective: SessionRetrospective) -> float:
+        if retrospective.verification_status == "passed":
+            return 0.9
+        if retrospective.verification_status == "skipped":
+            return 0.55
+        if retrospective.verification_status == "failed":
+            return 0.15
+        return 0.7 if retrospective.outcome == "completed" else 0.2
+
+
+def next_review_after(days: int = 7) -> datetime:
+    return datetime.now(UTC) + timedelta(days=days)