feat: add AI.INPUT.IM status auto switch

[zhuifengshaonian6]

Summary

• add a Codex++ user script that monitors status.input.im and selects the first healthy model by priority
• use the Codex native model callbacks and Electron fetch bridge, with browser fetch fallback
• require consecutive health confirmation for automatic switches and keep retrying after API failures
• provide a persistent 38px collapsed status control with pause, resume, and manual check actions
• register the script in index.json with a verified SHA-256

Validation

• node --check scripts/ai-input-im-status-auto-switch.js
• python -m json.tool index.json
• verified index SHA-256 matches the submitted script
• tested in Codex++ 1.2.47 on Windows: status request, current/target model discovery, native switch callback, pause/resume, and collapsed/expanded UI