refactor(cli): minor cleanups

[iuioiua]

Addresses #5607 (comment)

The following tests pass:

import { assertEquals } from "@std/assert";

Deno.test("isNumber should return true for valid numbers", () => {
  assertEquals(isNumber("123"), true);
  assertEquals(isNumber("-456"), true);
  assertEquals(isNumber("0"), true);
  assertEquals(isNumber("3.14"), true);
  assertEquals(isNumber("-2.5"), true);
  assertEquals(isNumber("1e3"), true);
  assertEquals(isNumber("-5e-2"), true);
  assertEquals(isNumber("0x10"), true);
});

Deno.test("isNumber should return false for invalid numbers", () => {
  assertEquals(isNumber("abc"), false);
  assertEquals(isNumber("123abc"), false);
  assertEquals(isNumber("12.34.56"), false);
  assertEquals(isNumber("1e"), false);
  assertEquals(isNumber("e3"), false);
  assertEquals(isNumber("0xg"), false);
  assertEquals(isNumber(""), false);
  assertEquals(isNumber("\t"), false);
  assertEquals(isNumber("-Infinity"), false);
  assertEquals(isNumber("Infinity"), false);
});

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.38%. Comparing base (ddfeff9) to head (cba62f3).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5628      +/-   ##
==========================================
- Coverage   96.38%   96.38%   -0.01%     
==========================================
  Files         466      466              
  Lines       37591    37588       -3     
  Branches     5541     5542       +1     
==========================================
- Hits        36231    36228       -3     
  Misses       1318     1318              
  Partials       42       42              

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[kt3k]

LGTM