test(state): align auth-data-root tests with trusted precomputed root semantics

[p0mvn]

Motivation

ironwood-main CI is red: the "revert v12" that merged with #411 changed check.rs to trust a supplied precomputed auth-data root (precomputed_auth_data_root.unwrap_or_else(|| block.auth_data_root())) instead of re-deriving and comparing it, but two tests asserting the old strict InvalidAuthDataRoot rejection merged unchanged and now fail:

• check::tests::vectors::block_commitment_binds_precomputed_auth_data_root_to_block_body
• prop::all_upgrades_and_wrong_commitments_with_fake_activation_heights (the bad-auth-root case)

Solution

Test-only change: align both tests with the trust semantics. Under trust, a forged precomputed root on an otherwise-valid header surfaces as InvalidChainHistoryBlockTxAuthCommitment (the header committed to the real root; the check recomputed the commitment from the forged one) — which still proves the supplied value is the one bound into the check, so the block is rejected either way.

• The vectors test is renamed to block_commitment_uses_the_precomputed_auth_data_root and asserts the exact commitment-mismatch error, including the recomputed hash from the forged root.
• The prop test's bad-auth-root case matches InvalidChainHistoryBlockTxAuthCommitment instead of InvalidAuthDataRoot, with a comment explaining why.

Note for reviewers: trusting the cache is only as strong as the writers of SemanticallyVerifiedBlock::auth_data_root; the crate-privacy hardening for that field from the (dropped) precompute branch is not on ironwood-main, so the field is currently pub. If we want the type-level guarantee back, that is a separate change.

Tests

• The two previously failing tests now pass; cargo test -p zebra-state is fully green (265 + 2), cargo fmt --all -- --check and cargo clippy -p zebra-state --all-targets -- -D warnings pass.

AI Disclosure

• AI tools were used: Claude for the test updates and PR description.

PR Checklist

• The PR title follows conventional commits format: type(scope): description
• The PR follows the contribution guidelines.
• This change was discussed in an issue or with the team beforehand.
• The solution is tested.
• The documentation and changelogs are up to date.

[v12-auditor]

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