Merge phase-2-master-queue-and-exporter into main

[google-labs-jules]

Merged the phase-2-master-queue-and-exporter branch into main, bringing in the clean hub scaffolding, evidence exporter, validator, and documentation. Also cleaned up accidental __pycache__ files. Verified with tests.

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PR created automatically by Jules for task 8191583569104278844 started by @cyserman

[google-labs-jules]

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