docs: Improve API error handling for toolbox-core client

[anubhav756]

Fixes #273

Problem

Currently, the SDK client unconditionally attempts to parse all API responses as JSON. If the remote server returns an error (e.g., 403 Forbidden due to an authentication failure, or 404 Not Found), the response body is often HTML or plain text, not JSON.

This leads to a low-level ContentTypeError, which masks the original, more informative error from the server (like the HTTP status and reason). Users are left with a confusing "response not parseable" message instead of knowing the true cause of the failure.

Solution

This PR introduces a check to validate the HTTP response status before attempting to parse its body.

If the response status is not 200 OK, the client now captures the status code, reason phrase, and the raw response body.
It then raises a RuntimeError that includes all of this valuable context.
This ensures that the actual error from the server is always surfaced to the user.

Before

aiohttp.client_exceptions.ContentTypeError: 403, message='Attempt to decode JSON with unexpected mimetype: text/html; charset=utf-8'

After

RuntimeError: API request failed with status 403 (Forbidden). Server response: Forbidden

[twishabansal]

Thanks for the change @anubhav756 ! I was wondering if we wanted to change this across other API requests. Perhaps, we could create a helper method and add it for API requests in methods like load_tool() too.

[anubhav756]

Thanks for the change @anubhav756 ! I was wondering if we wanted to change this across other API requests. Perhaps, we could create a helper method and add it for API requests in methods like load_tool() too.

Thanks for pointing that out! Added.