TST: relax noisy stream_velocity_z apogee tolerance

stream_velocity_z at apogee is a residual of the apogee-time estimation:
it is physically ~0 but swings by ~1e-4 m/s across platforms/NumPy
versions and atmosphere discretizations (e.g. -8.9e-8 on py3.10 with the
new ISA grid, -2.0e-4 with the old grid, +2.6e-4 on py3.14). The previous
atol=1e-5 was tighter than this numerical noise, making the assertion
flaky. Use atol=1e-3, which is physically negligible (vertical speed
peaks above 200 m/s) while still catching real regressions.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Gui-FernandesBR

tests/integration/simulation/test_flight.py

@@ -386,8 +386,13 @@ def test_freestream_speed_at_apogee(example_plain_env, calisto):
     """
     # NOTE: this rocket doesn't move in x or z direction. There's no wind.
     hard_atol = 1e-12
-    soft_atol = 1e-5
     soft_rtol = 1e-4
+    # stream_velocity_z at apogee is a numerically noisy ~0 quantity: it is a
+    # residual of the apogee-time estimation and swings by ~1e-4 across
+    # platforms/NumPy versions and atmosphere discretizations. Use a looser
+    # absolute tolerance for it (1e-3 m/s is physically negligible for a rocket
+    # whose vertical speed peaks above 200 m/s).
+    apogee_z_atol = 1e-3
     test_flight = Flight(
         environment=example_plain_env,
         rocket=calisto,
@@ -414,7 +419,7 @@ def test_freestream_speed_at_apogee(example_plain_env, calisto):
     npt.assert_allclose(
         test_flight.stream_velocity_z(test_flight.apogee_time),
         0.0,
-        atol=soft_atol,
+        atol=apogee_z_atol,
         rtol=soft_rtol,
     )
     npt.assert_allclose(