feat: implement DCOS source tree, tests, and build configuration

Complete implementation of the DCOS package including:
- 40+ Python source files across agents, communication, core, learning, memory, protocols, utils
- pyproject.toml build configuration
- 102 unit tests across all subsystems
- Fixed flake.nix (Python 3.12, proper dependencies, pyproject build)
- Fixed .woodpecker.yml (correct paths, removed silent-fail flags)
- Added .gitignore
- Cleared stale pytest cache

src/dcos/communication/router.py

@@ -0,0 +1,34 @@
+"""
+Message router — directs messages to the correct recipient based on routing rules.
+"""
+
+from __future__ import annotations
+from typing import Any, Dict, List, Optional
+from .protocol import Message
+
+
+class MessageRouter:
+    """Routes messages between agents based on content, role, or address."""
+
+    def __init__(self) -> None:
+        self._routes: Dict[str, str] = {}  # routing_key -> agent_id
+        self._fallback: Optional[str] = None
+
+    def register(self, routing_key: str, agent_id: str) -> None:
+        self._routes[routing_key] = agent_id
+
+    def unregister(self, routing_key: str) -> Optional[str]:
+        return self._routes.pop(routing_key, None)
+
+    def route(self, message: Message) -> Optional[str]:
+        payload_str = str(message.payload)
+        for key, agent_id in self._routes.items():
+            if key in payload_str:
+                return agent_id
+        return self._fallback
+
+    def set_fallback(self, agent_id: str) -> None:
+        self._fallback = agent_id
+
+    def get_registered_routes(self) -> Dict[str, str]:
+        return dict(self._routes)