Windows: codex-tui app test stack overflows on clean HEAD

Summary

On Windows, codex-tui can abort with STATUS_STACK_OVERFLOW when running the app::tests::attach_live_thread_for_selection_rejects_unmaterialized_fallback_threads test. This reproduces from a clean detached worktree at upstream HEAD, so it is not caused by unrelated local TUI skill-popup changes.

Environment

• OS: Windows
• Repo: openai/codex
• Clean HEAD tested: 6de6eaa0c ([4/4] Honor Streamable HTTP MCP placement (#18584))
• Test path used: short path under C:\Users\stefa\codex-clean-head-proof-* to avoid Windows path-length failures from deeper worktree paths

Reproduction

From a clean detached worktree at HEAD:

cd C:\Users\stefa\codex-clean-head-proof-8868\codex-rs
cargo test -p codex-tui app::tests::attach_live_thread_for_selection_rejects_unmaterialized_fallback_threads -- --test-threads=1

Actual Result

running 1 test
test app::tests::attach_live_thread_for_selection_rejects_unmaterialized_fallback_threads ...

thread 'app::tests::attach_live_thread_for_selection_rejects_unmaterialized_fallback_threads' has overflowed its stack
error: test failed, to rerun pass `-p codex-tui --lib`

Caused by:
  process didn't exit successfully: ... (exit code: 0xc00000fd, STATUS_STACK_OVERFLOW)

A full local run of cargo test -p codex-tui also aborts with the same class of stack overflow before the suite can complete.

Expected Result

The test should pass or fail with a normal assertion. It should not abort the process with a stack overflow.

Notes

This was separated from a focused TUI skill mention popup change because the failure reproduces on clean HEAD. Keeping this as its own issue should make the root cause easier to triage without mixing it into unrelated UI behavior changes.