fix(node): send Node requests through the shared Fetch transport

[roncodes]

Problem

In v2.0.0, NodeAdapter overrides request(method, url, options), but the inherited get() calls request(path, 'GET', {}, options). Under Node, every GET therefore went to <host>/<namespace>/GET, with the path sent as the HTTP method. NodeAdapter also read its constructor-time config, so headers added later with setHeaders (such as Customer-Token and Accept-Language) and host changes were dropped.

The existing test called each verb but didn't check the URL, method or headers, so it didn't catch this. Browsers and React Native use BrowserAdapter and were not affected. Node consumers were, and that includes the Storefront SDK once it depends on this package.

Fix

NodeAdapter now only adds its User-Agent header and inherits the browser Fetch transport. Every verb, the current host and namespace, and headers set later now behave the same as in BrowserAdapter.

Tests

• New regression test: Node GET, POST and DELETE go to the right URL with the right method and body, and send the Authorization, setHeaders and per-request headers plus the Node User-Agent.
• The test fails on main, with the GET going to https://api.test/v1/GET, and passes with this change.
• 35/35 tests pass with 100% coverage. Typecheck, lint and format checks are clean.
• Part of release/v2.1.0.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (b76e577) to head (8c4dc7f).
⚠️ Report is 1 commits behind head on release/v2.1.0.

Additional details and impacted files

@@               Coverage Diff                @@
##           release/v2.1.0       #46   +/-   ##
================================================
  Coverage          100.00%   100.00%           
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  Files                  17        17           
  Lines                 866       855   -11     
  Branches              144       143    -1     
================================================
- Hits                  866       855   -11     

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