Fix call_parse to reliably detect direct script execution

[ncoop57]

Summary

Replaces the fragile inspect.getmodule()-based __main__ check in call_parse with a dedicated _is_script_run() helper that correctly identifies direct script execution across all three invocation styles: python foo.py, python -m foo, and %run foo.py in notebooks. Also fixes in-process nested runners (nested=True), broken since the introduction of _in_call_parse.

Changes

• Add _is_script_run(frame): resolves and compares __file__ from globals against frame.f_code.co_filename to confirm the frame is the top-level body of a directly-run script — not an import or nested call.
• Factor argv parsing out of _f into _run_cli: auto-execution now calls it directly, since at that point we already know the file is a script entry point. Previously auto-exec re-entered _f, which infers what to do from its caller's frame — and on the auto-exec path that frame is call_parse itself, giving the wrong answer. This restores in-process nesting (a nested=True runner launching another script via runpy): the inner script parses the leftover sys.argv even while the outer runner holds _in_call_parse, which previously suppressed it.
• _f itself is unchanged: decorated functions calling each other still get plain calls (Handle nested call_parse #759), and interactive zero-arg calls (notebook cells, the REPL) remain plain calls rather than argv parses.
• Direct globals mutation: replaces setattr(mod, ...) with frame.f_globals[func.__name__] = _f to avoid the inspect.getmodule() call that could misidentify the calling context.

Motivation

The previous check could incorrectly fire (or fail to fire) when call_parse-decorated functions were imported into a __main__ module, or called programmatically from a script. Additionally, nested runners silently passed defaults instead of parsing leftover sys.argv, since the inner script's entry point was treated as a plain function call.