feat(ui): add cache hit rate to context sidebar last-message token breakdown (#1524)

* feat(ui): add cache hit rate to context sidebar with verified formula

Add a Cache Hit row to the last-assistant-message token breakdown in
the context sidebar. The percentage is computed by the new
computeCacheHitRate utility:

  cache.read / (input + cache.read + cache.write) x 100

The formula was verified against the SDK source
(packages/opencode/src/session/session.ts:getUsage), which reports
input as the non-cached portion only
(totalInputTokens - cacheReadInputTokens - cacheWriteInputTokens).

Also export sumTokenBreakdown from tokenUtils for reuse, and fix the
event-reducer test type errors (setDelta/getText helpers, toBeCloseTo
replacement).

Closes: #

* fix: wire i18n key for Cache Hit label, fix formatNumber type, drop unintended event-reducer changes

* chore: remove unused cacheHitRate and cacheHitRateTooltip i18n keys from en.ts

* fix: correct cache hit token display

* fix: add French cache hit label

---------

Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/lib/i18n/messages/en.ts

@@ -1158,6 +1158,7 @@ export const dict = {
   'contextSidebar.tokens.reasoning': 'Reasoning',
   'contextSidebar.tokens.cacheRead': 'Cache Read',
   'contextSidebar.tokens.cacheWrite': 'Cache Write',
+  'contextSidebar.tokens.cacheHit': 'Cache Hit',
   'contextSidebar.actions.copyJson': 'Copy JSON',
   'contextSidebar.actions.copy': 'Copy',
   'contextSidebar.actions.copied': 'Copied',

packages/ui/src/lib/i18n/messages/es.ts

@@ -1124,6 +1124,7 @@ export const dict: Record<I18nKey, string> = {
   "contextSidebar.tokens.reasoning": "Razonamiento",
   "contextSidebar.tokens.cacheRead": "Lectura de caché",
   "contextSidebar.tokens.cacheWrite": "Escritura de caché",
+  "contextSidebar.tokens.cacheHit": "Acierto de caché",
   "contextSidebar.actions.copyJson": "Copiar JSON",
   "contextSidebar.actions.copy": "Copiar",
   "contextSidebar.actions.copied": "Copiado",

packages/ui/src/lib/i18n/messages/fr.ts

@@ -1031,6 +1031,7 @@ export const dict = {
   'contextSidebar.tokens.reasoning': 'Raisonnement',
   'contextSidebar.tokens.cacheRead': 'Lecture du cache',
   'contextSidebar.tokens.cacheWrite': 'Écriture du cache',
+  'contextSidebar.tokens.cacheHit': 'Succès du cache',
   'contextSidebar.actions.copyJson': 'Copier JSON',
   'contextSidebar.actions.copy': 'Copie',
   'contextSidebar.actions.copied': 'Copié',

packages/ui/src/lib/i18n/messages/ko.ts

@@ -1161,6 +1161,7 @@ export const dict: Record<I18nKey, string> = {
   'contextSidebar.tokens.reasoning': '추론',
   'contextSidebar.tokens.cacheRead': '캐시 읽기',
   'contextSidebar.tokens.cacheWrite': '캐시 쓰기',
+  'contextSidebar.tokens.cacheHit': '캐시 적중',
   'contextSidebar.actions.copyJson': 'JSON 복사',
   'contextSidebar.actions.copy': '복사',
   'contextSidebar.actions.copied': '복사됨',

packages/ui/src/lib/i18n/messages/pl.ts

@@ -1322,6 +1322,7 @@ export const dict: Record<I18nKey, string> = {
   'contextSidebar.stats.user': 'Użytkownik',
   'contextSidebar.tokens.cacheRead': 'Odczyt cache',
   'contextSidebar.tokens.cacheWrite': 'Zapis cache',
+  'contextSidebar.tokens.cacheHit': 'Trafienie cache',
   'contextSidebar.tokens.input': 'Wejście',
   'contextSidebar.tokens.output': 'Wyjście',
   'contextSidebar.tokens.reasoning': 'Rozumowanie',

packages/ui/src/lib/i18n/messages/pt-BR.ts

@@ -1124,6 +1124,7 @@ export const dict: Record<I18nKey, string> = {
   "contextSidebar.tokens.reasoning": "Raciocínio",
   "contextSidebar.tokens.cacheRead": "Leitura de cache",
   "contextSidebar.tokens.cacheWrite": "Escrita de cache",
+  "contextSidebar.tokens.cacheHit": "Acerto de cache",
   "contextSidebar.actions.copyJson": "Copiar JSON",
   "contextSidebar.actions.copy": "Copiar",
   "contextSidebar.actions.copied": "Copiado",

packages/ui/src/lib/i18n/messages/uk.ts

@@ -1124,6 +1124,7 @@ export const dict: Record<I18nKey, string> = {
   "contextSidebar.tokens.reasoning": "Міркування",
   "contextSidebar.tokens.cacheRead": "Читання кешу",
   "contextSidebar.tokens.cacheWrite": "Запис кешу",
+  "contextSidebar.tokens.cacheHit": "Влучання в кеш",
   "contextSidebar.actions.copyJson": "Скопіювати JSON",
   "contextSidebar.actions.copy": "Копіювати",
   "contextSidebar.actions.copied": "Скопійовано",

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

@@ -1124,6 +1124,7 @@ export const dict: Record<I18nKey, string> = {
   'contextSidebar.tokens.reasoning': '推理',
   'contextSidebar.tokens.cacheRead': '缓存读取',
   'contextSidebar.tokens.cacheWrite': '缓存写入',
+  'contextSidebar.tokens.cacheHit': '缓存命中',
   'contextSidebar.actions.copyJson': '复制 JSON',
   'contextSidebar.actions.copy': '复制',
   'contextSidebar.actions.copied': '已复制',

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

@@ -1134,6 +1134,7 @@ export const dict: Record<I18nKey, string> = {
   'contextSidebar.tokens.reasoning': '推理',
   'contextSidebar.tokens.cacheRead': '快取讀取',
   'contextSidebar.tokens.cacheWrite': '快取寫入',
+  'contextSidebar.tokens.cacheHit': '快取命中',
   'contextSidebar.actions.copyJson': '複製 JSON',
   'contextSidebar.actions.copy': '複製',
   'contextSidebar.actions.copied': '已複製',