Clarify updater phases and recovery

[cauyxy]

Summary

• model checking, available, downloading, installing, ready-to-restart, restarting, and failed updater phases explicitly
• derive shell status, modal actions, priority, and dismissal policy from one updater snapshot
• replace native error copy with localized semantic updater problems and manual restart recovery
• expose determinate and indeterminate download progress accessibly
• update updater truth documentation and focused behavior coverage

Testing

• npm run check
• npx vitest run src/features/about/updater.test.ts src/features/about/updaterProblems.test.ts src/features/about/updaterPresentation.test.ts src/layouts/ShellUpdateModal.test.tsx src/layouts/ShellHeader.test.tsx
• npm run test:unit
• npm run verify -- --source-only
• Browser Preview: English/Chinese check status, timed recovery, focus, modal count, and horizontal overflow
• macOS Tauri smoke: startup detection completed; current 4.5.0 updater manifest reachable; frontend, overlay, and settings returned HTTP 200

Closes #29

Release Notes:

• 应用更新现在提供清晰的下载、安装与重启阶段，并在失败时给出本地化恢复指引。

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 5e2552b755

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

Use platform-neutral restart recovery copy

When the Windows updater path reaches the new restart-failure state, this same localized message is shown after impl.isWindows() and relaunch() rejects. In that scenario Windows users are told to reopen the app from “Applications”, which is macOS-only and leaves them with incorrect recovery instructions; split the restart failure copy by platform or make it neutral enough for both Windows and macOS.

Useful? React with 👍 / 👎.