Ensure the rule conversion leaves no metavariables

[aabounegm]

Closes #82

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PR-Codex overview

Detailed summary

• Added a new function objectHasMetavars to check if an object contains any metavariables.
• Added helper functions bindingHasMetavars and attrHasMetavars to check if a binding or attribute contains any metavariables.
• Updated the checkCond function to use the new objectHasMetavars function to check for metavariables in objects.

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