fix: clamp lower bound of arcsin argument in get_apparent_wind() to prevent silent NaN

[abhinavsudhik]

Related Issue / Discussion:

Fixes Issue #170

Changes:

• Modified direct_power_boat.py — added lower-bound clamp for arg_arcsin
  in get_apparent_wind() (lines 235–241)

Further Details:

Summary:

The get_apparent_wind() method computes arg_arcsin as the argument for np.arcsin(),
which requires its input to be within [-1, 1]. Due to floating-point rounding, arg_arcsin
can produce slightly below -1 (e.g. -1.0000000001).
To rectify this error , the values of arg_arcsin are clamped back to the bound.

Before: Only the upper bound (arg_arcsin > 1) was clamped. The lower bound
(arg_arcsin < -1) was unhandled, causing np.arcsin() to silently return NaN,
corrupting apparent wind angle, power, and fuel calculations.

After: A symmetric elif branch now clamps the lower bound to -1 when the
violation is within rounding tolerance (< 0.000001), consistent with the existing
upper-bound logic.

Dependencies:

No new dependencies required.

PR Checklist:

In the context of this PR, I:

• have (already previously) filled the 52North Contributor License Agreement
  and received positive feedback on this matter
• have filled the 52North Contributor License Agreement
  and am waiting for feedback
• provide unit tests embedded in the WRT test framework
  (WeatherRoutingTool/tests) that allow the simple testing of the
  new/modified functionalities. All (previous and new) unit tests
  execute without new error messages.
• ensure that the code formatter runs without errors/warnings
• ensure that my changes follow the WRT's guidelines for contributing
  at the time of the contribution