windows: verify raw pipe command parity

[anp-oai]

Intent

The raw Windows launcher changes a compatibility-sensitive process boundary. The stack should only complete after its observable command behavior matches the previous Tokio path across representative Windows cases.

Implementation

• Add a table-driven test-local Tokio reference launcher.
• Compare exit status, stdout, and stderr between Tokio and the raw launcher.
• Cover closed stdin, separate output streams, native exit code 37, Unicode environment and cwd values, tricky quoting and trailing backslashes, spaced executable paths, child PATH lookup, and .cmd/.bat dispatch.

Manual validation

• Cross-compiled the complete codex-utils-pty Windows test target with cargo +1.95.0 check --target x86_64-pc-windows-msvc -p codex-utils-pty --tests.

Stack

1. job primitives → 2. local ConPTY → 3. restricted sessions → 4. elevated runner → 5. command preparation → 6. raw pipe launcher → 7. command parity