Fix/dismissible infinite toasts (#1319)

* fix: make PWA install and OpenCode update toasts dismissible

Both 'Install OpenChamber' and 'OpenCode update available' toasts use
duration: Infinity with no close affordance, so they persist on screen
until the user accepts (install/update) or reloads the tab. For users
who do not want to install the PWA or upgrade right now, this is
intrusive and there is no opt-out.

Add a Dismiss button (sonner cancel action) to both toasts. When the
user dismisses:

- PWA: persist a flag in localStorage so the prompt does not reappear
  on future sessions. Accepting Install still works as before.
- OpenCode update: persist the dismissed version in localStorage. The
  toast will appear again only when a newer version becomes available.

Adds new i18n keys pwa.installPrompt.dismiss and
opencodeUpdate.toast.actions.dismiss across all seven locales (en,
es, ko, pl, pt-BR, uk, zh-CN).

* test: extract toast dedup helpers and cover with 28 unit tests

Lift the dismissal-decision logic out of usePwaInstallPrompt and
OpenCodeUpdateToast into a React-free sibling module so it can be
unit-tested directly. The React surfaces remain sole owners of side
effects (storage writes, toast.info, event listeners); the new module
only answers 'should we show?'.

New module openCodeUpdateDedup.ts exposes four helpers:
- shouldShowPwaInstallToast(input) - three gates: dismissed,
  sessionShown, hasActiveToast.
- shouldShowOpenCodeUpdateToast(input) - empty version, seen set,
  dismissed===version gates; a different dismissed version lets the
  toast resurface for the new release.
- resolveOpenCodeUpdateVersion(detail) - parses CustomEvent payloads
  defensively (null/non-object/non-string -> '').
- resolveOpenCodeUpgradeStatusVersion(status) - parses upgrade status
  payloads (status falsy / available!==true / latestVersion non-string
  -> '').

Consumers now call the helpers and only run the side-effect when the
decision is true. Behaviour is unchanged.

Coverage: 28 tests via bun:test, 33 expects, all pass first try.

packages/ui/src/lib/i18n/messages/zh-CN.ts

@@ -17,6 +17,7 @@ export const dict: Record<I18nKey, string> = {
   'common.revealPath.fileManager': '在文件管理器中打开',
   'pwa.installPrompt.description': '安装 OpenChamber 以便更快访问',
   'pwa.installPrompt.action': '安装',
+  'pwa.installPrompt.dismiss': '忽略',
   'pwa.installPrompt.started': '已开始安装',
   'pwa.installPrompt.installed': 'OpenChamber 已安装',
   'layout.mainTab.chat': '聊天',
@@ -2176,6 +2177,7 @@ export const dict: Record<I18nKey, string> = {
   'opencodeUpdate.toast.available.title': 'OpenCode 有可用更新',
   'opencodeUpdate.toast.available.description': '版本 {version} 已可安装。',
   'opencodeUpdate.toast.actions.update': '更新',
+  'opencodeUpdate.toast.actions.dismiss': '忽略',
   'opencodeUpdate.toast.actions.reload': '重载 OpenCode',
   'opencodeUpdate.toast.upgrading.title': '正在更新 OpenCode...',
   'opencodeUpdate.toast.upgrading.description': '请保持 OpenChamber 打开。',