fix(updater): persist update banner dismissal across restarts

[yexisu]

Problem

In manual update mode, the update banner's dismiss (×) button only wrote component-local React state (useState in UpdateBanner.tsx). Every app restart re-showed the same notice for a version the user had already declined (issue #1317, problem 1 — update dismissal not persisted). Problem 2 of that issue (asktool cards reappearing) is already fixed by #1309.

Fix

Record the dismissal durably instead of in component memory:

• New updatesDismiss IPC channel; UpdateBanner calls it when the user dismisses.
• AppUpdaterController.dismiss() stores the version and persists it via the existing host settings channel as updateDismissedVersion (mirrors the existing lastNotifiedUpdateVersion persistence wiring).
• UpdateState gains a dismissed flag; the banner hides from the pushed flag, so the decision survives restarts.
• When a newer version is discovered, the stale dismissal is cleared (in memory and in settings), so future releases keep notifying.
• host-core validate_settings_value validates the new key (non-empty string up to 128 chars, or null to clear), with regression tests.

Validation

• update-preference.test.mjs 6/6 pass (incl. new regression test asserting the banner consumes update.dismissed and calls api.updatesDismiss())
• auto-update.test.mjs 8/8 pass
• desktop tsc --noEmit clean; cargo fmt --check clean
• host-core unit tests require a local Rust linker; left to CI

Fixes #1317

[vastsa]

Thanks for the focused persistence change. The manual-mode reappearance is real, and saving the dismissed version addresses that path. I can’t merge this as a complete fix for #1317 yet: the issue also explicitly reports that dismissing in in-app mode should stop the background download. Here, dismiss() only sets the dismissed flag and persists the version; it leaves the updater in in-app mode with autoDownload enabled, so the download continues after the banner hides. Please cover that behavior with a controller-level regression test, or narrow the PR/issue claim so it does not mark the unresolved behavior fixed. This head also predates current main and needs refreshing before a landing review. Thanks for the work.

[vastsa]

Thanks for the original persistence fix. I completed the in-app path so dismissal also cancels the active download and prevents that release from restarting automatically. The maintainer follow-up #1339 has merged, with your original commit retained in its history. I’m closing this PR to avoid landing the same fix twice. Thanks for the contribution.

[vastsa]

The completed maintainer follow-up #1339 is merged.

[yexisu]

确认关闭合理：刚把分支对最新 main rebase 时发现上游已在 e356fb348 中落地了等价（且更完整——activeDownloadCancellation 真实取消进行中的传输）的 in-app dismiss 停止下载实现，连同 1f51acd69 的持久化路径，#1317 的两条行为都已覆盖。我的 0e0b5745e（downloadSuppressedFor 抑制方案）是冗余实现，不再推送。感谢接手与落地。