Propagate errors from custom pretty printers

[OskarEichler]

Problem: PPMethods#pp treats every NoMethodError raised by a custom pretty_print implementation as if the method were absent, silently replacing the failure with generic inspect output. This also hides missing methods called inside the printer and missing super implementations.

Fix: Fall back only when the missing call is exactly pretty_print on the object being rendered and a core respond_to? check confirms the method is absent. Internal printer errors continue to propagate.

Regression coverage: Adds an upstream regression that asserts both the raised exception and missing method name. The combined completion branch passes 42 tests / 64 assertions on Ruby 4.0.6 and 39 / 56 on Ruby 3.2, plus 510 focused model checks on each Ruby.