fix: array type flags (number/boolean/string) should respect their value

[chatman-media]

Fixes #415.

Problem

When an array option is configured with an object, the parser decides whether to coerce its values to number/boolean/string based on the presence of the corresponding key, ignoring its value. As a result a falsy type flag still enables coercion:

const parser = require("yargs-parser")

parser("--foo dog cat", { array: { key: "foo", number: false } })
// actual:   { _: [], foo: [ null, null ] }   (NaN on older versions)
// expected: { _: [], foo: [ "dog", "cat" ] }

parser("--foo dog cat", { array: { key: "foo", number: undefined } })
// same wrong result

The README documents enabling coercion with number: true, and the type definition declares these properties as boolean?, so false/undefined should behave as if the flag were absent. The same bug affects boolean: false (values wrongly coerced to booleans) and string: false (numbers wrongly kept as strings).

Cause

In lib/yargs-parser.ts, the assignment was derived from Object.keys(opt), which only checks key existence:

const assignment = Object.keys(opt).map(function (key) {
  const arrayFlagKeys = { boolean: "bools", string: "strings", number: "numbers" }
  return arrayFlagKeys[key]
}).filter(Boolean).pop()

Fix

Only enable a coercion flag when its value is strictly === true. (Also guards the object-vs-string opt case explicitly, instead of relying on a string`s numeric character indices never matching a flag name.)

Tests

Added four tests covering number: false, number: undefined, boolean: false, and string: false. All four fail on main and pass with the fix; the full suite (npm test) stays green (366 passing) with 100% coverage on yargs-parser.ts, and npm run check (gts lint) is clean.

[shadowspawn]

(Will be a while before I review this. Both the original code and replacement code are somewhat opaque, and other issues waiting.)