Implement `ShadeError` base exception class

[codebestia]

Description

All SDK-specific errors must inherit from a common ShadeError so callers can catch all SDK errors with a single except ShadeError. It should carry a human-readable message, the HTTP status_code (if applicable), and the raw response_body for debugging.

Proposed Steps

• Create src/shade/errors.py.
• Define ShadeError(Exception) with __init__(self, message, status_code=None, response_body=None).
• Add __str__ returning a formatted string including the status code when present.
• All other exceptions in this file must subclass ShadeError.

Acceptance Criteria

• except shade.ShadeError catches all SDK errors.
• str(error) includes both the message and the HTTP status code when present.
• error.response_body contains the raw API response as a string.
• ShadeError can be raised standalone (e.g. for contract-level errors with no HTTP context).

[Errordog2]

/attempt #15

Implemented the SDK error base class in #21: shade.ShadeError, HTTP context fields, package-root exports, and tests covering standalone/base/subclass behavior.

[nayt9]

Hello sir , my name is Nathan. I’m smart contract developer, and I’d love to contribute to this project. I’m comfortable working with modern frontend tools and blockchain technologies, and I can deliver tasks quickly often within 24 hours.
Please let me know how I can get started or if there are any issues suitable for a first contribution.