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/ko.ts

@@ -17,6 +17,7 @@ export const dict: Record<I18nKey, string> = {
   'common.revealPath.fileManager': '파일 관리자에서 열기',
   'pwa.installPrompt.description': '더 빠르게 접근하려면 OpenChamber를 설치하세요',
   'pwa.installPrompt.action': '설치',
+  'pwa.installPrompt.dismiss': '닫기',
   'pwa.installPrompt.started': '설치가 시작되었습니다',
   'pwa.installPrompt.installed': 'OpenChamber가 설치되었습니다',
   'layout.mainTab.chat': '채팅',
@@ -2210,6 +2211,7 @@ export const dict: Record<I18nKey, string> = {
   'opencodeUpdate.toast.available.title': 'OpenCode 업데이트 사용 가능',
   'opencodeUpdate.toast.available.description': '버전 {version}을 설치할 수 있습니다.',
   'opencodeUpdate.toast.actions.update': '업데이트',
+  'opencodeUpdate.toast.actions.dismiss': '닫기',
   'opencodeUpdate.toast.actions.reload': 'OpenCode 다시 로드',
   'opencodeUpdate.toast.upgrading.title': 'OpenCode 업데이트 중...',
   'opencodeUpdate.toast.upgrading.description': 'OpenChamber를 열어 두세요.',