Add unit coverage for protocol config and supply reads

[davedumto]

Summary

This PR adds focused unit coverage for the internal read paths behind protocol config lookup and creator supply lookup.

The new tests stay scoped to helper and read behavior only:

• verify the shared creator supply read helper returns the stored supply for an existing creator
• verify the shared creator supply read helper returns 0 when the creator does not exist
• verify the shared protocol config read path returns the stored config values
• verify protocol fee basis points can be read correctly from stored config

Implementation Notes

The new unit tests were added in creator-keys/src/test.rs and use env.as_contract(...) so the helper functions are exercised in a valid contract-storage context.

Snapshot fixtures generated for the new unit tests were included alongside the test changes.

Why This Matches The Issues

• keeps assertions focused on read/helper behavior
• covers both success and missing-creator cases for creator supply reads
• covers a successful protocol fee bps lookup
• introduces no contract behavior changes outside test coverage

Testing

• cargo test --workspace

Closes #80
Closes #81
Closes #83
Closes #85

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