Remove axios as a peer dependency #155

Summary

The SDK still requires axios as a peer dependency. Every resource method cancels through an axios CancelToken, configuration exposes axiosAdapter, and the README tells callers to use global axios interceptors. A major version should send HTTP with the platform fetch and stop importing axios.

Requirements

• The package manifest does not list axios as a dependency or a peer dependency, and SDK source does not import it.
• Browser and Node calls use fetch. Callers who only set configuration and call resource methods keep the same URLs, query strings, bearer tokens, and refresh behavior.
• requestOptions.cancelToken becomes requestOptions.signal (AbortSignal). A cancellation is distinguishable from OrderCloudError.
• SdkConfiguration.axiosAdapter is removed. Callers can supply a custom fetch and a request/response hook for logging, rewriting, or retrying.
• OrderCloudError keeps status, statusText, errorCode, errors, and isOrderCloudError. error.request is no longer an axios request object.
• The README, migration guide, and generated cancelToken docs describe the replacements.
• The default timeout stays the current configuration default (60 seconds).

This is a major-version break. It is specified separately from the open 14.0.0 release.

Spec: specs/001-remove-axios/spec.md