[架构讨论] PR #304 fix(codex): 修复正文消息无法流式输出 — 核心路径改动

## 背景

PR #304 修复 Codex 正文消息无法流式输出的问题，涉及核心路径改动约 162 行。

触发条件：`core-paths`（核心路径改动 162 行 ≥ 150 行阈值）

## 需要确认

请白名单成员确认本次核心路径改动的合理性与影响面。

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*由 review-pr 流程自动创建 · 关联 PR: #304*

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关联 PR:#304(作者 @ganlingyao);本 issue 由 review-pr 流程自动创建,用于先讨论该 PR 涉及的技术架构调整,聊清楚后 PR 会恢复审查。

Start by reading PR #304, which fixes Codex body-message streaming and changes about 162 lines in core paths. Review the affected flow and its impact surface; the architecture discussion is done when a whitelist member confirms the change is reasonable and the PR can resume review.

Written by the indexing model from the issue text.