Update stale VRT window clamping tests to match #1697 reject contract

[brendancol]

Summary

• After read_vrt: out-of-bounds window silently clamped instead of raising (drift from local/HTTP) #1697, read_vrt rejects any window outside the VRT extent with ValueError. Two tests in test_kwarg_behaviour_2026_05_12_v2.py still asserted the pre-read_vrt: out-of-bounds window silently clamped instead of raising (drift from local/HTTP) #1697 clamping behaviour and were failing.
• Renamed test_window_clamps_to_raster_bounds to test_window_out_of_bounds_raises and test_window_clamps_negative_offsets to test_window_negative_offsets_raise. Both now use pytest.raises(ValueError, match="outside the VRT extent"), matching the same contract read_to_array (open_geotiff eager path windowed read coord/data shape mismatch on out-of-bounds windows #1634) and _read_cog_http (HTTP eager COG read drops window and band, no PlanarConfiguration=2 handling #1669) already enforce.
• Test-only; no production code touched.

Test plan

• pytest xrspatial/geotiff/tests/test_kwarg_behaviour_2026_05_12_v2.py (23 passed)
• pytest xrspatial/geotiff/tests/ -k vrt (194 passed)
• Searched the rest of xrspatial/geotiff/tests/ for clamping assertions; no other tests assert the old behaviour.

Closes #1719

[Copilot]

Pull request overview

Updates stale VRT window-behavior tests to reflect the post-#1697 contract where read_vrt(..., window=...) rejects any out-of-bounds window with ValueError (instead of silently clamping).

Changes:

• Renamed two window tests to reflect the new “reject” behavior.
• Replaced clamping assertions with pytest.raises(ValueError, match="outside the VRT extent") for out-of-bounds windows (past-edge and negative offsets).

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[brendancol]

Superseded by #1731, which landed the same fix (different rename: test_window_outside_raster_bounds_rejected / test_window_negative_offsets_rejected rather than the names here). The conflict on rebase is exactly the duplicated test rewrite. Safe to close.