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_agents/test_ethics.py

@@ -0,0 +1,29 @@
+"""
+Tests for EthicsAgent.
+"""
+
+import pytest
+from dcos.agents.ethics import EthicsAgent, EthicalConstraint
+
+
+class TestEthicsAgent:
+    def test_validate_ethical(self):
+        agent = EthicsAgent()
+        result = agent.validate("help the user")
+        assert len(result) == 0
+
+    def test_validate_unethical(self):
+        agent = EthicsAgent()
+        result = agent.validate("deceive the user")
+        assert len(result) > 0
+
+    def test_add_constraint(self):
+        agent = EthicsAgent()
+        before = len(agent._constraints)
+        agent.add_constraint(EthicalConstraint.BENEFICENCE)
+        assert len(agent._constraints) == before  # already present
+
+    def test_act(self):
+        agent = EthicsAgent()
+        result = agent.act({"action": "help"})
+        assert result["ethical"] is True