Classify Codex background request operations

[fengjikui]

Summary

• classify Codex requests from protocol-native turn metadata
• separate main turns, subagents, compaction, and independent background memory extraction
• keep background prompts out of user input while preserving full responses for inspection
• preserve per-chain context deltas when background work interleaves with the main conversation

Evidence

• verified real requests #37, #38, and #39 from codex cli 捕获数据
• #38 is displayed as Codex 后台任务 · 记忆提取 and does not become a user turn
• #39 compares against #37 rather than the independent #38 request

Validation

• npm run release:check:macos
• real dashboard screenshot inspection at http://127.0.0.1:43110
• git diff --check