Fix northness/eastness to stay lazy on dask arrays (#1123)

* Add sweep-performance design spec

Parallel subagent triage + ralph-loop workflow for auditing all
xrspatial modules for performance bottlenecks, OOM risk under
30TB dask workloads, and backend-specific anti-patterns.

* Add sweep-performance implementation plan

7 tasks covering command scaffold, module scoring, parallel subagent
dispatch, report merging, ralph-loop generation, and smoke tests.

* Add sweep-performance slash command

* Fix northness/eastness to stay lazy on dask arrays (#1122)

Use da.cos/da.sin/da.deg2rad/da.where when the aspect result is dask-
backed, preventing implicit materialization via numpy dispatch.

Author: brendancol

xrspatial/aspect.py

@@ -506,8 +506,12 @@ def northness(agg: xr.DataArray,
     asp = aspect(agg, name='_aspect', method=method, z_unit=z_unit,
                  boundary=boundary)
     asp_data = asp.data
-    trig = np.cos(np.deg2rad(asp_data))
-    out = np.where(asp_data == -1, np.nan, trig)
+    if da is not None and isinstance(asp_data, da.Array):
+        trig = da.cos(da.deg2rad(asp_data))
+        out = da.where(asp_data == -1, np.nan, trig)
+    else:
+        trig = np.cos(np.deg2rad(asp_data))
+        out = np.where(asp_data == -1, np.nan, trig)
     return xr.DataArray(out,
                         name=name,
                         coords=agg.coords,
@@ -582,8 +586,12 @@ def eastness(agg: xr.DataArray,
     asp = aspect(agg, name='_aspect', method=method, z_unit=z_unit,
                  boundary=boundary)
     asp_data = asp.data
-    trig = np.sin(np.deg2rad(asp_data))
-    out = np.where(asp_data == -1, np.nan, trig)
+    if da is not None and isinstance(asp_data, da.Array):
+        trig = da.sin(da.deg2rad(asp_data))
+        out = da.where(asp_data == -1, np.nan, trig)
+    else:
+        trig = np.sin(np.deg2rad(asp_data))
+        out = np.where(asp_data == -1, np.nan, trig)
     return xr.DataArray(out,
                         name=name,
                         coords=agg.coords,