fix(tests): test_get_u and test_get_v are never collected by pytest and contain self-referential assertions

[pankaj-bind]

Bug

tests/test_weather.py contains two test functions - get_u and get_v - that pytest never collects or executes, providing zero coverage for WeatherCond.get_u() and WeatherCond.get_v().

Root cause (5 compounding defects)

1. Missing test_ prefix - pytest never discovers get_u / get_v
2. Parameter count mismatch - @parametrize declares 3 params, function signatures accept 2; would crash if collected
3. Self-referential assertions - assert u_test == pytest.approx(u_test) always passes regardless of correctness
4. Wrong expected values- e.g. get_u(45, 1) expects -1, actual is -sin(45°) = -0.7071…
5. Copy-paste error - get_v's parametrize string names the third param u_res instead of v_res

Impact

WeatherCond.get_u() and get_u.get_v() are used in production (apply_get_gauß). Any regression in wind-component decomposition goes completely undetected.

Expected behaviour

Both functions should be collected and executed by pytest with correct expected values.