Chat: use cached endpoint model ids before probing

tests/test_chat_cached_model_normalization.py

@@ -0,0 +1,20 @@
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+
+
+def test_chat_context_uses_cached_models_before_live_model_probe():
+    source = (ROOT / "routes" / "chat_helpers.py").read_text()
+
+    assert "def _normalize_model_id_from_cache" in source
+    assert "cached_models" in source
+    assert "norm = _normalize_model_id_from_cache(sess) or normalize_model_id" in source
+
+
+def test_cached_model_match_keeps_basename_normalization():
+    source = (ROOT / "routes" / "chat_helpers.py").read_text()
+
+    assert "def _match_cached_model_id" in source
+    assert "os.path.basename(requested.rstrip(\"/\"))" in source
+    assert "os.path.basename(model_id.rstrip(\"/\")) == req_base" in source