perf: find expose()'s caller from its frame instead of inspect.stack()

[lesnik512]

expose() found its caller's module with inspect.stack()[1].frame. inspect.stack() builds a FrameInfo for every frame on the stack and reads source lines for each one, only for the code to use the first frame. Called from a conftest during pytest collection, with 24 frames on the stack, that took 1.3 ms of the 1.5 ms one expose() call cost.

It now takes the caller's frame with sys._getframe(1) and still passes it to inspect.getmodule, so the exec() case keeps raising the same RuntimeError. One expose() call from a conftest drops from 1.524 ms to 0.030 ms.

sys._getframe trips ruff's SLF001, so the line carries a noqa. inspect.currentframe() would avoid it but can return None, which would need its own handling. ADR-0001 and the docstring said "via inspect.stack()" and now say "the calling frame".

This is a performance change only. The existing tests cover it, and all 27 pass with 100% coverage.