Fix TEXTGEN_AI_MODELS full-name mapping and unify model resolution

backend/services/llm_providers/routing_observability.py

@@ -0,0 +1,22 @@
+"""Structured observability helpers for LLM routing decisions."""
+
+from __future__ import annotations
+
+import hashlib
+import json
+from typing import Any, Dict, Optional
+
+
+def _mask_user_id(user_id: Optional[str]) -> str:
+    if not user_id:
+        return "anonymous"
+    return hashlib.sha256(str(user_id).encode("utf-8")).hexdigest()[:12]
+
+
+def emit_routing_event(logger, event: str, *, user_id: Optional[str] = None, **fields: Any) -> None:
+    payload: Dict[str, Any] = {
+        "event": event,
+        "tenant": _mask_user_id(user_id),
+        **fields,
+    }
+    logger.info("[llm_routing] {}", json.dumps(payload, sort_keys=True, default=str))