feat(hot-reload): Add HotModule dataclass and HotReloader registry

tests/test_hot_reloader.py

@@ -0,0 +1,35 @@
+from __future__ import annotations
+import pytest
+from src.hot_reloader import HotModule, HotReloader
+
+def test_hot_module_dataclass_fields():
+    hm = HotModule(
+        name="test_module",
+        file_path="/path/to/test_module.py",
+        state_keys=["attr1", "attr2"],
+        delegation_targets=["method_a", "method_b"],
+    )
+    assert hm.name == "test_module"
+    assert hm.file_path == "/path/to/test_module.py"
+    assert hm.state_keys == ["attr1", "attr2"]
+    assert hm.delegation_targets == ["method_a", "method_b"]
+
+def test_hot_reloader_register_and_get():
+    HotReloader.HOT_MODULES.clear()
+    hm = HotModule(name="test_mod", file_path="/fake/path.py", state_keys=[], delegation_targets=[])
+    HotReloader.register(hm)
+    assert "test_mod" in HotReloader.HOT_MODULES
+    assert HotReloader.HOT_MODULES["test_mod"] is hm
+
+def test_hot_reloader_register_duplicate_raises():
+    HotReloader.HOT_MODULES.clear()
+    hm1 = HotModule(name="dup", file_path="/a.py", state_keys=[], delegation_targets=[])
+    HotReloader.register(hm1)
+    with pytest.raises(ValueError, match="already registered"):
+        HotReloader.register(hm1)
+
+def test_hot_reloader_is_error_state():
+    HotReloader.HOT_MODULES.clear()
+    HotReloader.last_error = None
+    HotReloader.is_error_state = False
+    assert HotReloader.is_error_state is False