pyo3-ffi: add missing `Py_SET_REFCNT` binding

`test_super_traverse_early_return_does_not_abort` is flaky on free-threaded builds (~30% of runs)

pyo3-build-config: CONDA_PREFIX set but no valid Python interpreter causes build failure

polyfill for `cfg_select` does not emit the same code

Clarify newsfragment requirement

create_interface macro example from documentation does not produce usable classes when used inside pymodule

0.29 Release

`PyErr` conversion for `TryFromFloatSecsError` (and other missing stdlib errors?)

`getattr_opt` uses identity check instead of subclass check for `AttributeError` on Python < 3.13

`fixup_for_abi3_version` downgrades version causing wrong link library name when cross-compiling for Android