Problem Statement

PR #237 renamed Airfoil's leading-point identifiers to the Lp form required by docs/AXES_POINTS_AND_FRAMES.md, making outline_A_Lp and mcl_A_Lp the canonical public names. To keep that release non-breaking, it retained three aliases that emit DeprecationWarnings announcing removal in v6.0.0: the outline_A_lp constructor keyword (implemented with the module-level _UNSET sentinel) and the outline_A_lp and mcl_A_lp properties. The v6.0.0 release needs to complete the removal.

Location(s): pterasoftware/geometry/airfoil.py, tests/unit/test_airfoil.py, docs/CLASSES_AND_IMMUTABILITY.md

Proposed Solution

1. Delete the outline_A_lp constructor keyword from Airfoil.__init__, along with its sentinel branch, its DeprecationWarning, its docstring entry, and the module-level _UNSET sentinel.
2. Delete the deprecated outline_A_lp and mcl_A_lp properties.
3. Delete the TestAirfoilDeprecatedLpAliases class from tests/unit/test_airfoil.py.
4. Remove the note about the deprecated aliases from docs/CLASSES_AND_IMMUTABILITY.md.

Additional Context

This is a breaking API change for any caller still passing or reading the old names, which is why it is scheduled for the v6.0.0 major release and pre-announced with DeprecationWarnings, mirroring the approach used for #230 and #233.