Fix pdb breakpoint resolution for class methods

This change ensures that unresolved class-attribute breakpoints raise a 'not found' error instead of registering an incorrect target.

Author: cocolato

Misc/NEWS.d/next/Library/2025-11-25-16-00-29.gh-issue-59000.YtOyJy.rst

@@ -1,6 +1 @@
-Fix breakpoint resolution for class methods when the module is not imported.
-When setting a breakpoint such as ``break C.foo`` while the module that
-defines ``C`` has not yet been imported, ``pdb`` could previously resolve
-and bind the top‑level function ``foo`` incorrectly. This change ensures
-that unresolved class-attribute breakpoints raise a ``"not found"`` error
-instead of registering an incorrect target.
+Fix :mod:`pdb` breakpoint resolution for class methods when the module defining the class is not imported.