refactor: standardize error handling and raise ToolError per MCP policy

[ChinmayPande48]

Description

Note

This PR improves error handling across the Cloud Aura API MCP server to ensure compliance with the Anthropic MCP Directory Policy as suggested in issue #94
The previous implementation returned error dictionaries from the service layer, which does not align with MCP error-handling standards.

This update ensures:

• Service layer exceptions are no longer swallowed or converted into error dicts.
• MCP tools act as the error boundary and consistently raise ToolError.
• Stack traces are preserved using raise ... from e.

This aligns the server behavior with MCP Directory requirements for structured and predictable error responses.

Type of Change

• New feature
• Bug fix
• Breaking change
• Documentation update
• Project configuration change

Complexity

• LOW
• MEDIUM
• HIGH

Complexity:

The change required refactoring error propagation across multiple layers (API client → service layer → MCP tool layer) to ensure consistent and policy-compliant behavior without altering functional behavior.

How Has This Been Tested?

• Unit tests
• Integration tests
• Manual tests

Manual testing included:

• Triggering validation errors (e.g., invalid input parameters)
• Simulating API failures (invalid credentials, network errors)
• Verifying that tools now raise ToolError instead of returning error dictionaries
• Confirming proper logging and preserved exception chaining

Checklist

The following requirements should have been met (depending on the changes in the branch):

• Documentation has been updated
• Unit tests have been updated
• Integration tests have been updated
• Server has been tested in an MCP application
• CHANGELOG.md updated if appropriate