Add ChatGPT OAuth ASR live test

[yvette-carlisle]

Summary

• add a parser test for Codex ChatGPT OAuth auth.json shape
• add an ignored live ASR test that downloads an Open Speech Repository WAV sample
• assert ChatGPT OAuth ASR returns the expected Harvard sentence transcript
• stabilize the auth timeout helper test so CI does not depend on a sub-90ms scheduler window

Verification

• cargo test -p voxit-core providers::chatgpt::tests::
• cargo test -p voxit-core auth::tests::timeout_helper_stops_waiting_after_deadline
• VOXIT_RUN_CHATGPT_ASR_LIVE=1 cargo test -p voxit-core live_chatgpt_oauth_asr_transcribes_open_speech_sample -- --ignored --nocapture
• cargo make checks
• cargo +nightly fmt --all -- --check
• taplo fmt --check