tau2: module-level silencing (order-independent)

Function-level silencers kept losing the race to whichever 'import
tau2.*' fired first in the process. The filter + TAU2_DATA_DIR now
install when the env registry loads the plugin, strictly before any
tau2 import can happen anywhere.

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

evalharness/agent/envs/tau2_official.py

@@ -18,6 +18,25 @@ from typing import Any, Dict, List, Optional
 from ...data.sample import ChatMessage, Sample
 from ..loop import Environment, register_env
 
+# ---- module-level, order-independent tau2 silencing --------------------
+# Every function-level silencer proved fragile to import order (banners
+# fire at 'import tau2.*' wherever it first happens in the process).
+# This block runs when the ENV_REGISTRY loads this plugin -- strictly
+# before any tau2 import anywhere -- and is therefore the one that counts.
+import os as _os
+import sys as _sys
+
+_os.environ.setdefault('TAU2_DATA_DIR',
+                       '/data1/sora/evalscope/tools/tau2-bench/data')
+try:
+    from loguru import logger as _lg
+
+    _lg.remove()
+    _lg.add(_sys.stderr, level='ERROR')
+except Exception:
+    pass
+# ------------------------------------------------------------------------
+
 _PATCHED = False