fix(anvil): serialize rollback against mining to stop a mine-race panic

[gomesalexandre]

anvil_rollback/anvil_reorg could unwind the chain while a concurrent multi-block evm_mine_detailed call was still mining, because do_mine_block takes the mining lock per-block but rollback never took it at all.

Depending on exactly when the rollback landed, this surfaced as one of two things:

• A confusing BlockNotFound mid-mine - an in-flight mine_one losing the parent it was building on.
• An attempt to subtract with overflow panic in evm_mine_detailed's post-mining block lookup (crates/anvil/src/eth/api.rs), which reads best_number() once mining finishes and assumes it's still at least mined_blocks - 1 higher than the height before the call started.

Fix

• Backend::rollback now holds the same self.mining lock do_mine_block already takes, so it can't interleave with an in-flight mine.
• evm_mine_detailed uses checked_sub instead of a bare subtraction when re-deriving each mined block's number from the post-mining height, skipping a block number that no longer exists instead of panicking or wrapping. This is defense in depth - the chain height can still move between individual mine iterations, not just around the rollback lock - so it's kept even with the lock fix.

Verification

Added evm_mine_detailed_handles_concurrent_rollback: a multi-threaded-runtime test that races evm_mine_detailed(blocks: 50) against repeated anvil_rollback calls.

• Against the original code: reliably fails, showing both failure modes above (BlockNotFound before the lock fix, then the arithmetic panic once only the lock fix was applied and the narrower post-loop race was exposed).
• With both fixes applied: passes consistently across repeated runs.

cargo test -p anvil --lib for the touched modules (eth::api::tests, plus the existing rollback-related backend test) all green.

receipts

$ cargo test -p anvil --lib "eth::api::tests"
running 7 tests
test eth::api::tests::fractional_reward_percentiles_use_cache_resolution ... ok
test eth::api::tests::shortened_pre_fork_fee_history_uses_upstream_start ... ok
test eth::api::tests::fee_history_rejects_invalid_reward_percentiles ... ok
test eth::api::tests::fee_history_is_complete_when_cache_entries_are_missing ... ok
test eth::api::tests::evm_mine_detailed_handles_concurrent_rollback ... ok
test eth::api::tests::memory_reset_stages_live_fees_after_active_mining ... ok
test eth::api::tests::set_rpc_url_installs_context_equivalent_identity_with_new_instance ... ok
test result: ok. 7 passed; 0 failed; 0 ignored; 0 measured; 120 filtered out

$ cargo test -p anvil --lib rollback
test eth::backend::mem::storage::tests::test_remove_block_states_on_rollback ... ok
test eth::api::tests::evm_mine_detailed_handles_concurrent_rollback ... ok
test result: ok. 2 passed; 0 failed

🤖 Generated with Claude Code

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