fix: resolve failing tests in TS utility library

[stooit]

Summary

Fixes all 16 failing tests across the utility library and implements missing functionality. All 60 tests now pass (0 failures); no test files modified and no dependencies added.

Changes

• src/calculator.ts — divide now throws Error("Division by zero") instead of returning Infinity.
• src/string-utils.ts — wordCount uses trim().split(/\s+/) so consecutive spaces no longer inflate the count; truncate implemented (respects maxLength budget incl. ellipsis, breaks at word boundary, hard-cuts when no space, handles maxLength smaller than ellipsis).
• src/task-manager.ts — implemented remove (returns false for unknown id), update (title/priority, returns false for unknown id), and sortBy for priority (high>medium>low), createdAt (oldest first), and status.
• src/date-utils.ts — fixed off-by-one in formatRelative (Math.round instead of Math.floor; 36h now reads "2 days ago").
• src/validator.ts — isEmail accepts long TLDs; isUrl accepts URLs with a port (e.g. http://localhost:3000).

Testing

bun test → 60 pass, 0 fail.

Assumptions

• sortBy("status") uses alphabetical order as the tests assert.
• formatRelative uses round-to-nearest semantics, matching the test expectations.
• Reviewed by the review subagent: all fixes confirmed as genuine root-cause corrections.

🤖 Generated autonomously.