MWPW-200785 [Lingo] Stop reading the international cookie in sign-in region resolution

[vhargrave]

Split off from #6268 (MWPW-200345). Per Shane Do, acomCountry is not a CCHome requirement yet (Akamai-only shipped), so the acomLocale/acomCountry split is shelved. This PR carries only the small, low-risk half we want to land now.

Resolves: MWPW-200785

What changes

getLingoRegion({ useGeoLocation: true }) no longer consults sessionStorage.international / the international cookie. On the sign-in path the Lingo region now resolves from the user's geo (physical location) only — matching the Akamai redirect and webps's implementation.

   if (!regions || !Object.keys(regions).length) return null;

-  if (useGeoLocation) {
-    const intlPrefix = sessionStorage.getItem('international') || getCookie('international');
-    if (intlPrefix) return Object.values(regions).find((r) => r.prefix === `/${intlPrefix}`) ?? null;
-  }
-
   const country = useGeoLocation
     ? normCountryCode(await getCountry())
     : (await resolveDetectedMarketCountry())?.toLowerCase();

Why: under Lingo the international cookie holds only the language (not a region), so it is no longer meaningful for sign-in region resolution. Resolving from geo makes the sign-in path emit the same region as the Akamai redirect, giving CCH/Adobe Home one consistent contract.

Scope / non-changes

• The default (no-arg) getLingoRegion path used by MEP/content is unchanged (still the selected-market country cookie).
• The Adobe Home redirect param shape is unchanged (stays acomLocale=<region-prefix> as on stage today). The acomCountry split lives in the shelved MWPW-200345 [Lingo] Split Adobe Home redirect into acomLocale + acomCountry #6268.
• Non-Lingo locales are unchanged.

Tests

• test/utils/utils.test.js — getLingoRegion with useGeoLocation now ignores the international cookie and resolves from geo (both the "diverges" and "no region" cases); the loadIms redirect test asserts geo wins over a divergent international cookie.
• test/blocks/susi-light-login/susi-light-login.test.js — sign-in widget locale follows geo, ignoring the international and market cookies.
• Full npm test: 3691 passed; the only failure is the known fetchAndProcessPlainHtml with MEP gnav network flake (fails identically on clean stage, unrelated to this change).

Test URLs

• Before (stage): https://www.stage.adobe.com/fr/products/photoshop.html?martech=off&akamaiLocale=ch&country=ch
• After (branch): https://www.stage.adobe.com/fr/products/photoshop.html?martech=off&milolibs=vhargrave-lingo-drop-international-cookie&akamaiLocale=ch&country=ch

Steps to test:
set your international cookie to lu_fr using the region picker in the footer for example and notice how it has no impact on the after url anymore. You'll be taken to https://www.stage.adobe.com/home?acomLocale=ch_fr instead of https://www.stage.adobe.com/home?acomLocale=lu_fr

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Commits

• 6c8cd37 ✅ (latest)