- Replace O(n) while-loops in dateAdd() with O(1) modular arithmetic
- Implement overflow option handling in dateFromFields, yearMonthFromFields, monthDayFromFields
- Add fields() method per Temporal Calendar Protocol
- Extract shared borrow logic from dateUntil() into borrowHijriDiff helper
- Replace magic number 1444 with REFERENCE_YEAR constant
- Convert test suites to node:test runner with describe/it blocks
- Add tests for dateUntil, dateAdd with days/weeks, overflow reject/constrain, fields(), yearMonthFromFields, monthDayFromFields
- Add ESLint + Prettier with typescript-eslint config
- Add lint job to CI workflow
- Add noImplicitReturns and noFallthroughCasesInSwitch to tsconfig
- Disable unused sourcemap generation in tsup
- Update .editorconfig to include .mts and .cts extensions
- Add missing AI agent dirs to .gitignore