Tidy streamstats fix per /simplify review

Per /simplify review on PR #245:
- Replace `json.loads(r.text)` with `r.json()` (matching the convention
  used in `nldi.py` and `nwis.py`) and drop the now-unused `import
  json` from `dataretrieval/streamstats.py`.
- Remove the dead `format == "shape"` branch — a stale Fiona-stub
  (`# use Fiona to return a shape object` + `pass`) that silently fell
  through to `Watershed.from_streamstats_json(data)`. The docstring no
  longer mentions `"shape"` so removing the branch matches the contract.
- Drop four trivial unit tests that each exercised a one-line behavior
  change obvious from the diff (`from_streamstats_json` returns an
  instance, `format="object"` returns a dict, `__init__` populates self,
  `_workspaceID` alias resolves). Keep the load-bearing one:
  `test_from_streamstats_json_does_not_mutate_class` guards against
  re-introducing the class-mutation antipattern under refactor.

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

Author: thodson-usgs

dataretrieval/streamstats.py

@@ -5,8 +5,6 @@
 
 """
 
-import json
-
 import requests
 
 
@@ -137,11 +135,7 @@ def get_watershed(
     if format == "geojson":
         return r
 
-    if format == "shape":
-        # use Fiona to return a shape object
-        pass
-
-    data = json.loads(r.text)
+    data = r.json()
 
     if format == "object":
         return data

tests/streamstats_test.py

@@ -1,8 +1,6 @@
 """Tests for the streamstats module."""
 
-import json
-
-from dataretrieval.streamstats import Watershed, get_watershed
+from dataretrieval.streamstats import Watershed
 
 SAMPLE_JSON = {
     "featurecollection": [
@@ -14,12 +12,6 @@
 }
 
 
-def test_from_streamstats_json_returns_instance():
-    """Watershed.from_streamstats_json must return an instance, not the class."""
-    w = Watershed.from_streamstats_json(SAMPLE_JSON)
-    assert isinstance(w, Watershed)
-
-
 def test_from_streamstats_json_does_not_mutate_class():
     """Two watersheds must not share state via class-level attributes."""
     other_json = {
@@ -39,31 +31,3 @@ def test_from_streamstats_json_does_not_mutate_class():
     assert w2.parameters[0]["code"] == "OTHER"
     assert w1.watershed_point["id"] == "pt-1"
     assert w2.watershed_point["id"] == "pt-2"
-
-
-def test_get_watershed_object_returns_dict(requests_mock):
-    """get_watershed(format='object') must return parsed JSON, not None."""
-    url = "https://streamstats.usgs.gov/streamstatsservices/watershed.geojson"
-    requests_mock.get(url, text=json.dumps(SAMPLE_JSON))
-
-    result = get_watershed("NY", -74.524, 43.939, format="object")
-    assert isinstance(result, dict)
-    assert result["workspaceID"] == "NY20240101000000000"
-
-
-def test_watershed_init_populates_instance(requests_mock):
-    """Watershed(...) must populate the instance (regression: previously discarded)."""
-    url = "https://streamstats.usgs.gov/streamstatsservices/watershed.geojson"
-    requests_mock.get(url, text=json.dumps(SAMPLE_JSON))
-
-    w = Watershed("NY", -74.524, 43.939)
-    assert w.workspace_id == "NY20240101000000000"
-    assert w.parameters[0]["code"] == "DRNAREA"
-    assert w.watershed_point["id"] == "pt-1"
-    assert w.watershed_polygon["id"] == "poly-1"
-
-
-def test_workspace_id_back_compat_alias():
-    """Legacy `_workspaceID` attribute should still resolve."""
-    w = Watershed.from_streamstats_json(SAMPLE_JSON)
-    assert w._workspaceID == w.workspace_id == "NY20240101000000000"