Fix bugs on MCP tools PRESS0-3489

[crodriguezbrito]

Proposed changes

This PR fix a fatal error if the tools don't return an array on execute_callback.

[ERROR] Error calling tool | Context: {"tool":"blu-add-cpt","exception":"WP\MCP\Handlers\Tools\ToolsHandler::handle_tool_call(): Return value must be of type array, WP_Post returned"}

The callback result is now encapsulated in an array. This, along with replacing WP_Error objects with a standard array format ("message" => "problem description"), prevents the following error.

[ERROR] Error calling tool | Context: {"tool":"blu-get-cpt","exception":"WP\MCP\Handlers\Tools\ToolsHandler::handle_tool_call(): Return value must be of type array, WP_Error returned"} | User ID: 1

Also this PR add the reassign parameter as required for the "blu/delete-user" ability.

Jira task

Type of Change

Production

• Bugfix (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)
• Dependency update
• Refactoring / housekeeping (changes to files not directly related to functionality)

Development

• Tests
• Dependency update
• Environment update / refactoring
• Documentation Update

Visual

Checklist

• I have read the CONTRIBUTING doc
• I have viewed my change in a web-browser
• Linting and tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments