Update snarkVM version to 4.12.0 and bump devnode to 0.4.0

[iamalwaysuncomfortable]

Motivation

Bump snarkVM from 4.11.0 to 4.12.0 (released October 13, 2026) and release devnode 0.4.0.

The upstream v4.11.0...v4.12.0 diff is large (toolchain 1.96, RocksDB secondary instances, Varuna/KZG internals, parser hardening), but only a handful of changes reach this crate:

• The history feature is gone. It was enabled in Cargo.toml and no longer exists, so it is dropped. snarkVM also removed the per-height mapping record that VM::evaluate_view_at_height read from, so views at a past height can no longer be evaluated by anyone (snarkOS answers the route with 404 in its history compatibility mode). POST /program/{id}/view/{function}/{height} is kept so clients that read /block/height/latest and pass that height keep working: it evaluates when height is the latest height and answers 404 (500 under the legacy prefixes) with a pointer to the latest-height route otherwise. The check is repeated after evaluation so a concurrent auto-mode block advance cannot return results for a different height.
• StorageMode::Custom gained a second field in aleo-std-storage 1.0.4 (optional path for opening RocksDB as a read-only secondary). The devnode always owns its ledger and passes None. The declared dependency is bumped to 1.0.4 since snarkVM pins it exactly.
• The ledger now applies spend and synthesis limits to beacon blocks itself (Subdag::min_spend_limit / Authority::beacon_limits, the upstream version of the logic this crate mirrored from snarkVM PR #3350). beacon_block_limits now delegates to Authority::beacon_limits, and the unit test that asserted snarkVM accepts an over-limit beacon block is updated: snarkVM now aborts the overflowing deployment on its own, matching what the devnode pre-filter already reported.
• Testnet MAX_CERTIFICATES drops to 40 at V22 and the table grows from 5 to 6 entries. The beacon-limit test used the last entry while evaluating at V18, so it now looks up the value active at V18. The 40-validator genesis is within the new limit.
• Consensus heights: V21/V22 are now scheduled on mainnet and testnet. TEST_CONSENSUS_VERSION_HEIGHTS is unchanged, so the devnode still boots to V22 at height 25.
• MSRV is now 1.96; CI uses stable, so no workflow change.

Not relevant to the devnode: slipstream plugins removed, new dev_genesis_state_root feature, MAX_MAPPINGS raised to 128 at V22, rand.chacha cost change.

Test Plan

• cargo fmt --all -- --check: clean.
• cargo test --locked: 7 unit tests and 6 integration tests pass.
• New unit test test_view_at_height_only_serves_the_latest_height covers the 404 for a non-latest height and evaluation at the latest height.
• docs/rest-api.md documents the view routes and the height restriction.

Related PRs

• Update snarkVM version to 4.11.0 and bump devnode to 0.3.0 #37 (snarkVM 4.11.0 bump)