starknet_transaction_prover,starknet_os,workspace: run the circuit verifier as a bootloader task

[einat-starkware]

Part 6 of the single-proof verification stack — this PR closes the milestone loop: a single transaction's proof is verified by the real Cairo1 circuit verifier, and the verifier's output digest is checked against the value the OS emits.

• run_circuit_verifier_task: runs the privacy circuit verifier executable as a single simple-bootloader task on the transaction's processed proof and parses the bootloader's output page ([1, 10, verifier_program_hash, digest words 0..7]).
• verify_circuit_verifier_task_output: recomputes the expected verification digest from the packed values the OS emits (apollo_starknet_os_program,starknet_os,blockifier: emit the single-proof digest in the OS output #15064) and compares, after checking the verifier program hash against a pinned value.
• Fixture: the proving side's processing of the golden leaf, generated with stwo_run_and_prove_recursive_tree at proving commit b75d21f9 under the canonical_small registry. Its output digest matches the Rust compute_processed_proof_output_digest bit for bit, and the end-to-end test passes: bootloader-run verifier digest == digest recomputed from the transaction's proof facts. Invalid-proof, wrong-program-hash and wrong-digest paths are covered.

Stack: #15090 ← #15091 ← #15092 ← #15064 ← #15086 ← this PR ← #15095.

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https://claude.ai/code/session_01XmPJM3Wph4QLmFmhcxVsh4

[reviewable-StarkWare]

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PR Summary

High Risk
Introduces end-to-end circuit proof verification and digest binding to OS output; mistakes here would accept invalid proofs or reject valid ones.

Overview
Adds verifier_task to the transaction prover so a transaction’s processed proof is verified by running the Cairo1 circuit verifier as a simple-bootloader task via cairo-program-runner-lib, then parsing the bootloader output (program hash + verification digest).

verify_circuit_verifier_task_output ties that run to OS facts: it checks the pinned verifier program hash, unpacks the OS’s packed processed-proof output digest, recomputes the expected verification digest with compute_verification_digest, and compares it to the verifier output. unpack_output_digest (inverse of pack_output_digest) lives in proof_fact_fold with round-trip tests.

Workspace Cargo.lock changes pin cairo-program-runner-lib 1.3.1 for the prover while keeping 2.4.0 on the proving stack, plus transitive hashbrown bumps on proving crates. Integration tests use gzipped fixtures (bootloader, verifier executable, golden processed proof) and cover success, wrong hash/digest, and corrupted proof failure.

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