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/schemas/skills.py

@@ -0,0 +1,38 @@
+from __future__ import annotations
+
+from datetime import datetime, timezone
+from typing import Any, Literal
+
+from pydantic import BaseModel, Field
+
+
+SkillStatus = Literal["candidate", "shadow", "active", "deprecated", "retired"]
+SkillInjectionMode = Literal["metadata_only", "summary", "full"]
+
+
+class SkillShortlistEntry(BaseModel):
+    skill_name: str
+    source: str = "runtime"
+    source_id: str | None = None
+    status: SkillStatus = "active"
+    scope: list[str] = Field(default_factory=list)
+    effectiveness: float | None = None
+    score: float = 0.0
+    rationale: str | None = None
+    summary: str | None = None
+    matched_terms: list[str] = Field(default_factory=list)
+    injection_mode: SkillInjectionMode = "metadata_only"
+    metadata: dict[str, Any] = Field(default_factory=dict)
+
+
+class SkillActivationRecord(BaseModel):
+    skill_name: str
+    source: str = "runtime"
+    source_id: str | None = None
+    status: SkillStatus = "active"
+    injection_mode: SkillInjectionMode = "metadata_only"
+    matched_terms: list[str] = Field(default_factory=list)
+    rationale: str | None = None
+    activated_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
+    outcome: str | None = None
+    metadata: dict[str, Any] = Field(default_factory=dict)