fix(fmt): handle missing group separator for 1000.1 in some locales

[IgorM867]

In some locales there is no group separator in parts which cause error during tests.

const parts = new Intl.NumberFormat().formatToParts(1000.1);
console.log(parts);
const group = parts.find(({ type }) => type === "group")!.value;

[
  { type: "integer", value: "1000" },
  { type: "decimal", value: "," },   
  { type: "fraction", value: "1" }   
]
error: Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'value')
const group = parts.find(({ type }) => type === "group")!.value;

Change to 10000.1 fix this issue.

const parts = new Intl.NumberFormat().formatToParts(10000.1);
console.log(parts);
const group = parts.find(({ type }) => type === "group")!.value;

[
  { type: "integer", value: "10" },
  { type: "group", value: " " },
  { type: "integer", value: "000" },
  { type: "decimal", value: "," },
  { type: "fraction", value: "1" }
]

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.58%. Comparing base (ae7048f) to head (4ad5309).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6117   +/-   ##
=======================================
  Coverage   96.58%   96.58%           
=======================================
  Files         536      536           
  Lines       40679    40679           
  Branches     6110     6110           
=======================================
  Hits        39291    39291           
  Misses       1344     1344           
  Partials       44       44           

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[lionel-rowe]

This still won't make the tests fully locale independent — at a minimum, it'll fail for locales like hi-IN that use lakhs and crores.

There's currently only one test that uses group, so something like this could work to replace it:

import { format } from "./bytes.ts";
import { assertEquals } from "@std/assert";
import { stub } from "@std/testing/mock";

Deno.test("format() handles group separators", async (t) => {
  const tests: { locale: string; expected: string }[] = [
    { locale: "en-US", expected: "1,000,000 YB" },
    // narrow non-breaking space
    { locale: "fr-FR", expected: "1\u202f000\u202f000 YB" },
    { locale: "es-ES", expected: "1.000.000 YB" },

    // https://en.wikipedia.org/wiki/Indian_numbering_system
    { locale: "hi-IN", expected: "10,00,000 YB" },
    { locale: "gu-IN", expected: "10,00,000 YB" },
  ];

  for (const { locale, expected } of tests) {
    await t.step(locale, () => {
      const toLocaleString = Number.prototype.toLocaleString;
      using _ = stub(
        Number.prototype,
        "toLocaleString",
        function (l) {
          return toLocaleString.call(this, l ?? locale);
        },
      );

      // explicitly supplying the locale
      assertEquals(format(1e30, { locale }), expected);
      // using the default locale (mocked with stub)
      assertEquals(format(1e30, { locale: true }), expected);
    });
  }
});