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