维护者确认：#2688 CodeModeOnly 限定到网关路由

PR https://github.com/makecindy/cindy/pull/2688 改了 Codex 路由、目录类型和 session/base-agent 相关契约，约 2100 行。这是核心路径上的路由/目录结构调整，需要维护者确认架构边界。\n\n确认方式：同意就在 PR 上 Approve；需要改就 Request Changes，作者改完后再 Approve。

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关联 PR:#2688(作者 @horizon554);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,维护者确认后 PR 会恢复推进。

Review PR #2688 first, focusing on its Codex routes, directory types, and session/base-agent contracts. This issue is for a maintainer to approve the architecture or request changes; it is done when the PR receives the appropriate review decision and can resume.

Written by the indexing model from the issue text.