apollo_starknet_os_program: add qm31 blake

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• apollo_starknet_os_program: calculate bootloader output hash in the OS #14123
• apollo_starknet_os_program: add qm31 blake #14121 👈 (View in Graphite)
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• Started at 2026-05-20T14:08:54Z
• Started at 2026-05-20T14:32:59Z

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PR Summary

Medium Risk
Introduces new Cairo0 hashing logic and cross-language parity tests; risk is mainly around subtle serialization/mod-reduction mismatches that could break downstream verifier assumptions. Changes are otherwise isolated to test-program compilation and test coverage.

Overview
Adds a new Cairo0 test program qm31_blake that computes a Blake2s-256 digest over QM31 inputs (serialized as 4 LE u32 limbs per element) and reduces the 8 digest words modulo 2^31-1.

Wires this program into the test-program build (compile_program.rs + QM31_BLAKE_BYTES) and adds a Rust reference implementation plus a parity test in blake2s_test.rs to assert Cairo output matches the expected QM31 hashing semantics across several cases.

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