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

tests/test_core/test_registry.py

@@ -0,0 +1,46 @@
+"""
+Tests for the AgentRegistry.
+"""
+
+import pytest
+from dcos.core.registry import AgentRegistry, AgentRecord
+
+
+class TestAgentRegistry:
+    def test_register_and_get(self):
+        registry = AgentRegistry()
+        record = AgentRecord(agent_id="a1", name="test-agent", role="planner")
+        registry.register(record)
+        retrieved = registry.get("a1")
+        assert retrieved is not None
+        assert retrieved.name == "test-agent"
+
+    def test_unregister(self):
+        registry = AgentRegistry()
+        record = AgentRecord(agent_id="a2", name="removable", role="researcher")
+        registry.register(record)
+        removed = registry.unregister("a2")
+        assert removed is not None
+        assert registry.get("a2") is None
+
+    def test_find_by_role(self):
+        registry = AgentRegistry()
+        registry.register(AgentRecord(agent_id="a1", name="planner-1", role="planner"))
+        registry.register(AgentRecord(agent_id="a2", name="planner-2", role="planner"))
+        registry.register(AgentRecord(agent_id="a3", name="researcher", role="researcher"))
+        planners = registry.find_by_role("planner")
+        assert len(planners) == 2
+
+    def test_find_by_capability(self):
+        registry = AgentRegistry()
+        registry.register(AgentRecord(agent_id="a1", name="capable", role="planner", capabilities=["ml", "nlp"]))
+        registry.register(AgentRecord(agent_id="a2", name="other", role="researcher", capabilities=["search"]))
+        ml_agents = registry.find_by_capability("ml")
+        assert len(ml_agents) == 1
+        assert ml_agents[0].agent_id == "a1"
+
+    def test_count(self):
+        registry = AgentRegistry()
+        assert registry.count() == 0
+        registry.register(AgentRecord(agent_id="a1", name="only", role="planner"))
+        assert registry.count() == 1