GitLab

refactor: merge RecordUsage and RecordUsageWithLongContext into shared core

- Extract recordUsageCore with recordUsageOpts for parameterized differences
- RecordUsage (276 lines) → thin wrapper (~40 lines)
- RecordUsageWithLongContext (251 lines) → thin wrapper (~20 lines)
- Split billing logic into calculateSoraMediaCost, calculateImageCost,
  calculateTokenCost sub-functions
- Extract buildRecordUsageLog for usage log construction
- Net reduction: -79 lines, eliminated ~170 lines of duplication