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_memory/test_conversation.py

@@ -0,0 +1,35 @@
+"""
+Tests for ConversationMemory.
+"""
+
+import pytest
+from dcos.memory.conversation import ConversationMemory
+
+
+class TestConversationMemory:
+    def test_create_conversation(self):
+        mem = ConversationMemory()
+        conv = mem.create("conv_1", ["agent_a", "agent_b"])
+        assert conv.conversation_id == "conv_1"
+        assert len(conv.participants) == 2
+
+    def test_add_turn(self):
+        mem = ConversationMemory()
+        mem.create("conv_1", ["alice", "bob"])
+        turn = mem.add_turn("conv_1", "alice", "Hello Bob!")
+        assert turn is not None
+        assert turn.content == "Hello Bob!"
+
+    def test_get_history(self):
+        mem = ConversationMemory()
+        mem.create("conv_1", ["a", "b"])
+        mem.add_turn("conv_1", "a", "msg1")
+        mem.add_turn("conv_1", "b", "msg2")
+        history = mem.get_history("conv_1")
+        assert history is not None
+        assert len(history) == 2
+
+    def test_missing_conversation(self):
+        mem = ConversationMemory()
+        assert mem.add_turn("nonexistent", "a", "msg") is None
+        assert mem.get_history("nonexistent") is None