feat(llm): añade factory que selecciona proveedor según settings

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/unit/test_llm_factory.py

@@ -0,0 +1,20 @@
+"""Tests del factory LLM."""
+
+import pytest
+
+from agentforge_core.config import Settings
+from agentforge_core.llm.factory import build_llm_provider
+from agentforge_core.llm.mock import MockProvider
+
+
+def test_factory_devuelve_mock_por_defecto() -> None:
+    s = Settings(llm_provider="mock", _env_file=None)  # type: ignore[call-arg]
+    p = build_llm_provider(s)
+    assert isinstance(p, MockProvider)
+    assert p.name == "mock"
+
+
+def test_factory_azure_requiere_credenciales() -> None:
+    s = Settings(llm_provider="azure", _env_file=None)  # type: ignore[call-arg]
+    with pytest.raises(ValueError):
+        build_llm_provider(s)