[codex] stabilize Prompt Optimize UI and transport

[weiadou]

Summary

• release Prompt Optimize 1.0.3 with revision-owned DOM selectors so legacy instances cannot remove the current button, style, settings panel, toast, or host;
• keep the sparkle button externally anchored before the model selector instead of participating in the action-row flex layout, and recompute that anchor on resize;
• retain native Electron fetch as the preferred transport, LLM Bridge compatibility fallback, cancellation, and redacted upstream errors.

Root cause

Repeated user-script injection and an inline flex insertion allowed stale Prompt Optimize instances to compete for shared DOM nodes and styles. That produced flicker, layout compression, cancelled-looking states, and an unreliable right-click surface.

Validation

• node --check scripts/prompt-optimize.js
• node --test tests/prompt-optimize-prosemirror-writer.test.js (10/10)
• git diff --check
• live Codex++ reload: 1.0.3 / v1-0-3-anchor
• live right-click opens the centered settings panel without a request
• live resize event retains ✨ → model → send with no loading state or request

No API configuration, Key, or real optimization request is included in this change.