Add agent and skill system: implement Agent and Skill classes, register media and naked agents, and create media_info demo skill

agents/naked.py

@@ -0,0 +1,15 @@
+"""
+naked agent — a barebone LLM with no extra skills attached.
+Just a thin wrapper that instructs the LLM to be a general helpful assistant.
+"""
+
+from agents import Agent, register
+
+naked_agent = Agent(
+    agent_id="naked",
+    description="A plain LLM — no extra skills, just a helpful assistant.",
+    skills=[],  # no skills
+    base_prompt="You are a helpful, general-purpose assistant.",
+)
+
+register(naked_agent)