fix: implement missing utils and fix edge-case bugs to pass all tests

[stooit]

Summary

Fixes all 16 previously-failing tests across the utility library. The full suite is now 60 pass / 0 fail, with no test files modified and no new dependencies added.

Changes

• src/calculator.ts — divide now throws Error("Division by zero") instead of returning Infinity.
• src/string-utils.ts
  • wordCount collapses consecutive whitespace (trim().split(/\s+/)) so empty tokens aren't counted.
  • truncate implemented: word-boundary truncation with the ellipsis counted toward maxLength.
• src/task-manager.ts — implemented/completed remove, update, and sortBy (priority weighting + createdAt oldest-first).
• src/date-utils.ts — formatRelative rounds hours→days (fixes the off-by-one; 36h → "2 days ago").
• src/validator.ts — isEmail accepts long TLDs (e.g. .museum); isUrl accepts explicit ports (e.g. http://localhost:3000).

Testing

bun test → 60 pass, 0 fail, 70 expect() calls.

Review notes / assumptions

• Scope was kept to exactly what the tests require, per task constraints.
• Independent review flagged non-blocking, untested edge cases for potential follow-up (not addressed here to stay in scope): truncate with very small maxLength (≤3), the 12-hour rounding boundary in formatRelative, and a pre-existing in-place mutation in TaskManager.update.

🤖 Generated autonomously