维护者确认: PR #1296 fix(desktop): preserve materialized steer ack after epoch bump

PR [#1296](https://github.com/makecindy/cindy/pull/1296) 触发维护者确认门。

**触发类别:** product
**触发原因:** 命中 UI 路径（apps/desktop/src/renderer/__tests__/pendingQueueDefer.test.ts / apps/desktop/src/renderer/lib/makerChatStore.ts）
**作者:** 1614080902102

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请任一维护者在 PR 上 Approve 以放行；需要修改请 Request Changes，作者改完后重新 Approve 即放行。

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关联 PR:#1296(作者 @1614080902102);本 issue 由 review-pr 流程自动创建,用于先讨论该 PR 涉及的产品 / UI 变更,维护者确认后 PR 会恢复推进。

Start with PR #1296 and inspect apps/desktop/src/renderer/__tests__/pendingQueueDefer.test.ts and apps/desktop/src/renderer/lib/makerChatStore.ts. Run the named test to understand the existing behavior around the epoch bump and materialized steer acknowledgement. The work is done when the PR has maintainer approval and can resume.

Written by the indexing model from the issue text.