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

agents/__init__.py

@@ -0,0 +1,64 @@
+"""
+Agent system — each agent combines a base LLM with optional skills
+to produce tailored system prompts and behavior.
+
+An Agent is a lightweight wrapper:
+- agent_id    : unique name (e.g. "naked", "media-agent")
+- description : human-readable summary
+- skills      : list of skill names to load
+- base_prompt : default system prompt (optional — falls back to generic)
+"""
+
+from dataclasses import dataclass, field
+from typing import Dict, List
+
+from skills import Skill, get_combined_prompt, list_all as list_all_skills
+
+
+@dataclass
+class Agent:
+    agent_id: str
+    description: str = ""
+    skills: List[str] = field(default_factory=list)
+    base_prompt: str = "You are a helpful agent."
+
+    def build_system_prompt(self) -> str:
+        """Combine base_prompt with all registered skills' prompt fragments."""
+        return get_combined_prompt(self.skills, base_prompt=self.base_prompt)
+
+    def __repr__(self) -> str:
+        sk = ", ".join(self.skills) if self.skills else "none"
+        return f"Agent(id={self.agent_id!r}, skills=[{sk}])"
+
+
+# ---------------------------------------------------------------------------
+# Global agent registry
+# ---------------------------------------------------------------------------
+_agent_registry: Dict[str, Agent] = {}
+
+
+def register(agent: Agent) -> None:
+    """Register an agent so it can be looked up by agent_id."""
+    _agent_registry[agent.agent_id] = agent
+
+
+def get(agent_id: str) -> Agent | None:
+    """Return a registered agent by id, or None."""
+    return _agent_registry.get(agent_id)
+
+
+def list_all() -> Dict[str, Agent]:
+    """Return a shallow copy of the registry."""
+    return dict(_agent_registry)
+
+
+def load_all_agents() -> None:
+    """
+    Import all agent modules so they self-register.
+    Call this once at startup.
+    """
+    import agents.naked         # noqa: F401
+    import agents.media_agent   # noqa: F401
+
+    # Also import skill modules so they self-register
+    import skills.media_info    # noqa: F401