Walkthrough

Adds Windows CRT-backed file-descriptor operations to the NT stdlib: get_inheritable(fd), dup(fd), and dup2(fd, fd2, inheritable), plus FFI declarations for _dup and _dup2, a Dup2Args struct, and helper logic to set/clear descriptor inheritable state and map errors to Python exceptions.

Changes

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

• Single-file change with cohesive additions.
• Review focus:
  • FFI signatures for _dup / _dup2
  • Correct handle conversion and raw_set_handle_inheritable usage
  • Error handling and resource cleanup in close_fd_and_raise
  • Dup2Args pyarg defaults and parsing

Possibly related PRs

• Rework crt_fd to be more aligned with io-safety #5789 — Touches the same vm/src/stdlib/nt.rs area and CRT-backed fd/handle inheritance refactor; likely closely related to these additions.

Poem

🐰 I hopped through bytes with a whiskered grin,

I cloned a handle on a midnight spin.
dup and dup2, a neat little trick,
inheritable flags set — click by click.
Carrots for code, and a floppy FD tin.

Pre-merge checks and finishing touches

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