Generalize Claude 5h auto-ping into a provider-generic scheduler and add
opt-in Codex auto-ping that warms the next 5h window via a tiny gpt-5.5
request when session.resetAt slides. Default off, per-connection toggle,
failure cooldown, blocking-quota skip, drains stream before success.
Closes#2107
Co-authored-by: Cursor <cursoragent@cursor.com>
