feat: add frozen Agent/Message/Thread types (id-keyed)

tests/test_types.py

@@ -0,0 +1,24 @@
+import uuid
+from agentmsgs.core.types import Agent, Thread, Message
+import datetime
+
+def test_agent_identity_on_id_not_name():
+    a1 = Agent(id=uuid.uuid4(), name="Alice")
+    a2 = Agent(id=uuid.uuid4(), name="Alice")
+    assert a1 != a2  # different id => not equal even though name same
+    assert hash(a1) != hash(a2)
+
+def test_agent_hash_on_id():
+    uid = uuid.uuid4()
+    a1 = Agent(id=uid, name="Alice")
+    a2 = Agent(id=uid, name="Bob")  # same id, different name => equal per design (id is identity)
+    assert a1 == a2
+    assert hash(a1) == hash(a2)
+
+def test_thread_multiple_with_same_participants_allowed():
+    a = Agent(id=uuid.uuid4(), name="A")
+    b = Agent(id=uuid.uuid4(), name="B")
+    t1 = Thread(id=uuid.uuid4(), participants=frozenset({a,b}), created_at=datetime.datetime.now(datetime.timezone.utc))
+    t2 = Thread(id=uuid.uuid4(), participants=frozenset({a,b}), created_at=datetime.datetime.now(datetime.timezone.utc))
+    assert t1 != t2
+    assert t1.participants == t2.participants