fix(contract): Clarify error message for invalid function name

[gap-editor]

Description

This PR improves the readability of the error message thrown by the callContract tool when an invalid ABI is provided.

Previously, the custom error message and the underlying system error were concatenated directly, making the output confusing and difficult to parse visually during debugging. This change adds an "Error: " prefix to the underlying error, clearly separating our contextual message from the system's error details.

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Screenshots (if appropriate):