Test composite gate truth tables

[gquar]

Add getPrimaryInputBindings() and getPrimaryOutputs() to Circuit to resolve a build dependency for GraphvizExporter.

The build failed because GraphvizExporter was attempting to use these non-existent methods on Circuit. This was discovered while attempting to run tests to diagnose a user's JUnit import error. Adding these methods allows the project to compile and tests to run successfully.

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[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
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