nldi: raise ValueError (not TypeError) for invalid navigation mode

`_validate_navigation_mode` raised `TypeError` for an invalid string
value (e.g. "ABC"). The sister helper `_validate_data_source` in the
same file already raises `ValueError` for the same kind of bad-input
case. `TypeError` is reserved for cases where an argument's type is
wrong; an unrecognized navigation-mode string is a value error.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: thodson-usgs

dataretrieval/nldi.py

@@ -486,7 +486,7 @@ def _validate_data_source(data_source: str):
 def _validate_navigation_mode(navigation_mode: str):
     navigation_mode = navigation_mode.upper()
     if navigation_mode not in ("UM", "DM", "UT", "DD"):
-        raise TypeError(f"Invalid navigation mode '{navigation_mode}'")
+        raise ValueError(f"Invalid navigation mode '{navigation_mode}'")
 
 
 def _validate_feature_source_comid(

tests/nldi_test.py

@@ -1,7 +1,9 @@
+import pytest
 from geopandas import GeoDataFrame
 
 from dataretrieval.nldi import (
     NLDI_API_BASE_URL,
+    _validate_navigation_mode,
     get_basin,
     get_features,
     get_flowlines,
@@ -280,3 +282,9 @@ def test_search_for_features_by_lat_long(requests_mock):
     assert search_results["features"][0]["type"] == "Feature"
     assert search_results["features"][0]["geometry"]["type"] == "LineString"
     assert len(search_results["features"][0]["geometry"]["coordinates"]) == 27
+
+
+def test_validate_navigation_mode_invalid_raises_value_error():
+    """Invalid navigation mode is a bad value, not a bad type -> ValueError."""
+    with pytest.raises(ValueError, match="Invalid navigation mode"):
+        _validate_navigation_mode("XX")