feat(guardrails): añade NeMo stub, CompositeEngine paralelo y factory

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

core/src/agentforge_core/guardrails/composite.py

@@ -0,0 +1,38 @@
+"""Engine que ejecuta varios sub-engines en paralelo y agrega resultados."""
+
+from __future__ import annotations
+
+import asyncio
+from typing import Any
+from uuid import UUID
+
+from agentforge_core.domain.guardrail import GuardrailViolation
+from agentforge_core.domain.policy import PolicyDefinition
+from agentforge_core.guardrails.base import GuardrailEngine
+
+
+class CompositeGuardrailEngine:
+    """Compone varios GuardrailEngine y agrega sus violaciones."""
+
+    name = "composite"
+
+    def __init__(self, engines: list[GuardrailEngine]) -> None:
+        if not engines:
+            raise ValueError("CompositeGuardrailEngine requiere al menos un engine.")
+        self._engines = engines
+
+    async def validate_input(
+        self, payload: str, policy: PolicyDefinition, trace_id: UUID
+    ) -> list[GuardrailViolation]:
+        results = await asyncio.gather(
+            *(e.validate_input(payload, policy, trace_id) for e in self._engines)
+        )
+        return [v for sub in results for v in sub]
+
+    async def validate_output(
+        self, payload: dict[str, Any], policy: PolicyDefinition, trace_id: UUID
+    ) -> list[GuardrailViolation]:
+        results = await asyncio.gather(
+            *(e.validate_output(payload, policy, trace_id) for e in self._engines)
+        )
+        return [v for sub in results for v in sub]

core/src/agentforge_core/guardrails/factory.py

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+"""Factory que ensambla el GuardrailEngine según settings."""
+
+from __future__ import annotations
+
+from agentforge_core.config import Settings
+from agentforge_core.guardrails.base import GuardrailEngine
+from agentforge_core.guardrails.composite import CompositeGuardrailEngine
+from agentforge_core.guardrails.guardrails_ai import GuardrailsAIEngine
+from agentforge_core.guardrails.nemo import NeMoGuardrailsEngine
+
+
+def build_guardrail_engine(settings: Settings) -> GuardrailEngine:
+    """Ensambla el engine: GuardrailsAIEngine siempre; NeMo si está habilitado."""
+    engines: list[GuardrailEngine] = [GuardrailsAIEngine()]
+    if settings.guardrails_nemo_enabled:
+        engines.append(
+            NeMoGuardrailsEngine(
+                allowed_keywords=[
+                    "sip",
+                    "ims",
+                    "cscf",
+                    "sbc",
+                    "mos",
+                    "hss",
+                    "registro",
+                    "incidente",
+                    "voz",
+                    "codec",
+                    "rollback",
+                ],
+            )
+        )
+    return CompositeGuardrailEngine(engines)

core/src/agentforge_core/guardrails/nemo.py

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+"""Stub de NeMo Guardrails. Solo se carga si GUARDRAILS_NEMO_ENABLED=true.
+
+En MVP se entrega como capa adicional de topical rails. La integración Colang
+completa queda documentada en docs/futuro.md como evolución natural.
+"""
+
+from __future__ import annotations
+
+from datetime import UTC, datetime
+from typing import Any
+from uuid import UUID
+
+import structlog
+
+from agentforge_core.domain.guardrail import GuardrailViolation
+from agentforge_core.domain.policy import PolicyDefinition
+
+log = structlog.get_logger(__name__)
+
+
+class NeMoGuardrailsEngine:
+    """Implementación mínima: detecta off-topic vía heurística básica.
+
+    Cuando se active la integración Colang real, este engine cargará un YAML
+    de configuración y delegará a ``nemoguardrails.LLMRails``. Por ahora aplica
+    una regla simple: si el input no menciona ninguno de los keywords de
+    ``allowed_keywords``, marca off-topic con severity warning.
+    """
+
+    name = "nemo"
+
+    def __init__(self, allowed_keywords: list[str] | None = None) -> None:
+        self._allowed = [k.lower() for k in (allowed_keywords or [])]
+
+    async def validate_input(
+        self, payload: str, policy: PolicyDefinition, trace_id: UUID
+    ) -> list[GuardrailViolation]:
+        if not self._allowed:
+            return []
+        lower = payload.lower()
+        if any(k in lower for k in self._allowed):
+            return []
+        log.info("nemo_offtopic", trace_id=str(trace_id))
+        return [
+            GuardrailViolation(
+                trace_id=trace_id,
+                timestamp=datetime.now(UTC),
+                stage="input",
+                validator="NeMoTopicalRails",
+                severity="warning",
+                message="Input fuera de los temas permitidos.",
+                blocked=False,
+            )
+        ]
+
+    async def validate_output(
+        self, payload: dict[str, Any], policy: PolicyDefinition, trace_id: UUID
+    ) -> list[GuardrailViolation]:
+        return []