fix(io): fall back to plain input on prompt_toolkit PermissionError

[FOWEPJF255]

Summary

• Catch PermissionError / OSError from prompt_session.prompt in confirm_ask and prompt_ask (Windows socketpair / WinError 10013).
• Clear prompt_session and fall back to builtins.input so file-mention confirms no longer crash.
• Add regression tests for the fallback path.

Fixes #5695

Test plan

• python -m pytest tests/basic/test_io.py::TestInputOutput::test_confirm_ask_falls_back_when_prompt_session_raises_permission_error tests/basic/test_io.py::TestInputOutput::test_prompt_ask_falls_back_when_prompt_session_raises_permission_error -q
• Manual: on Windows with a denied socketpair, trigger a confirm prompt and verify plain-input fallback instead of an uncaught exception

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}