feat(observability): logging JSON estructurado con structlog y trace_id

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

core/src/agentforge_core/observability/logging.py

@@ -0,0 +1,43 @@
+"""Configuración de logging estructurado JSON con propagación de trace_id."""
+
+from __future__ import annotations
+
+import logging
+import sys
+
+import structlog
+from structlog.contextvars import bind_contextvars, clear_contextvars
+
+
+def configure_logging(level: str = "INFO") -> None:
+    """Configura structlog para emitir JSON a stdout, una línea por evento."""
+    logging.basicConfig(
+        format="%(message)s",
+        stream=sys.stdout,
+        level=getattr(logging, level),
+        force=True,
+    )
+    structlog.configure(
+        processors=[
+            structlog.contextvars.merge_contextvars,
+            structlog.processors.add_log_level,
+            structlog.processors.TimeStamper(fmt="iso"),
+            structlog.processors.StackInfoRenderer(),
+            structlog.processors.format_exc_info,
+            structlog.processors.JSONRenderer(),
+        ],
+        wrapper_class=structlog.make_filtering_bound_logger(getattr(logging, level)),
+        context_class=dict,
+        logger_factory=structlog.PrintLoggerFactory(),
+        cache_logger_on_first_use=True,
+    )
+
+
+def bind_trace_id(trace_id: str) -> None:
+    """Añade trace_id al contexto actual; aparece en todos los logs siguientes."""
+    bind_contextvars(trace_id=trace_id)
+
+
+def clear_trace_id() -> None:
+    """Limpia el contexto al final del request."""
+    clear_contextvars()