fix: update Codex compatibility and renderer performance

[szguicheng]

Summary

This PR focuses on two areas:

1. Update compatibility with the latest Codex UI

Codex has changed its main UI structure, native field names, and theme/runtime surface contracts. This PR updates Codex++ to recognize and work with the latest Codex UI, including:

• Modern main-surface, thread, header, message, composer, and scrolling structures.
• The current Codex theme variables and Dream Skin API mapping.
• Modern composer and thread lifecycle behavior.
• Correct native field matching and state mapping, so existing theme behavior follows the right Codex UI state.
• Safe cleanup and idempotent marker reconciliation when Codex changes or remounts UI sections.

2. Significantly improve Codex renderer performance

Previously, enabling the Codex++ renderer could make the entire Codex page feel noticeably sluggish. This PR substantially reduces renderer overhead by:

• Coalescing repeated DOM scans and deferred work.
• Avoiding redundant inline-style, attribute, text, and dataset writes.
• Reducing unnecessary layout reads and repeated alignment work.
• Throttling retry paths and preventing duplicate event-listener installation.
• Making conversation alignment incremental and stable instead of repeatedly resetting layout.
• Narrowing mutation observation to changes that can actually affect layout or behavior.

The result is a much lower renderer workload and a substantially smoother Codex UI when Codex++ is enabled.

No visual style is hard-coded into the application by this PR; theme appearance remains controlled by the theme layer.

Validation

• npm test: 121 passed
• cargo test -p codex-plus-core --test dream_skin_package --test dream_skin_runtime --test cdp_bridge: 131 passed, 1 ignored
• node --check assets/inject/renderer-inject.js
• npm run vite:build
• cargo build --release --target aarch64-apple-darwin
• Local validation against Codex 26.825.32147

Related historical context: #1755 and #1881.