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_semantic.py

@@ -0,0 +1,27 @@
+"""
+Tests for SemanticMemory.
+"""
+
+import pytest
+from dcos.memory.semantic import SemanticMemory
+
+
+class TestSemanticMemory:
+    def test_add_and_get_fact(self):
+        mem = SemanticMemory()
+        mem.add_fact("dog", "species", "canine")
+        assert mem.get_fact("dog", "species") == "canine"
+
+    def test_add_relationship(self):
+        mem = SemanticMemory()
+        mem.add_relationship("dog", "wolf")
+        related = mem.get_related("dog")
+        assert "wolf" in related
+        assert "dog" in mem.get_related("wolf")
+
+    def test_query(self):
+        mem = SemanticMemory()
+        mem.add_fact("cat", "species", "feline")
+        mem.add_fact("lion", "species", "feline")
+        results = mem.query("species", "feline")
+        assert len(results) == 2