Sleeping fake Git processes and assumed HTTP frame boundaries made streaming
checks depend on scheduler timing. Hold fake Git behind an owned loopback
gate until the test observes the expected prefix; collect bytes independently
of frame splits and explicitly release subprocess progress.
Keep terminal-flush, promotion and cleanup ordering assertions. Gate waits
have bounded deadlines; no production streaming code changes are included.
Validation: all three git_response_streaming tests passed.
Assisted-by: Codex (GPT-6)