The recordTokenUsage function previously only persisted the aggregate tokensUsed
total, discarding the input/output breakdown that was already available via
getUsageTotals(). This meant token-usage.json had no per-record IO split,
making it impossible to analyse input vs output token costs in dashboards.
Changes:
- Add inputTokens, outputTokens, cacheReadTokens, cacheWriteTokens optional
fields to TokenUsageRecord type in usage-log.ts (new file)
- Write these fields (when non-zero) into each usage entry
- Fields are omitted (not null) when unavailable, keeping existing records valid
- Wire up recordTokenUsage() call in attempt.ts after llm_output hook
This is a purely additive change; existing consumers that only read tokensUsed
are unaffected.
