fix: NTT over-limit mint locks down the asset instead of reverting

[mrq1911]

Fixes #1511.

An over-limit NTT mint on the currencies precompile now takes the same reserve-and-lockdown path as an over-limit XCM deposit, instead of reverting MintLimitReached() and stranding source-chain funds until the window rolls.

Root cause → the precompile did a read-only IssuanceIncreaseFuse::can_mint pre-check and reverted over the limit. But the deposit it performs already routes through orml_tokens, whose PostDeposit hook is the circuit breaker (CurrencyHooks::PostDeposit = IssuanceIncreaseFuse, runtime/hydradx/src/assets.rs:130; orml_tokens fires it in do_deposit). So the pre-check was a redundant guard that short-circuited before the breaker's own reserve-and-lockdown could engage.

Fix → drop the can_mint pre-check (+ its now-dead import) from mint. The deposit then behaves exactly like the XCM path:

• over the per-period budget → the mint lands, the excess is reserved on the recipient, the asset goes into LockdownStatus::Locked(until) and AssetLockdown is emitted;
• into an already-locked asset → the deposit lands but the full amount is reserved (LockdownActive);
• within budget → unchanged.

The VAA is consumed (no replay), the recipient's excess is reserved rather than stuck on the source chain, and the safety mechanism the limit exists for actually engages.

Tests (integration-tests/src/evm.rs, currency_precompile_ntt) — updated the three that asserted the old revert:

• mint_over_the_limit_should_reserve_excess_and_lock_down_the_asset — 600 clean, then 500 over the 1,000 budget → 1,100 minted, 100 reserved, asset Locked.
• mint_into_a_locked_down_asset_reserves_the_full_amount — mint into a locked asset succeeds but fully reserves.
• burn_should_refill_mint_budget_within_period — reframed to net accounting (600 mint, burn 400, 700 stays within 1,000, no lockdown).

cargo test -p runtime-integration-tests currency_precompile_ntt → 14 passed / 0 failed; cargo fmt --check clean.

Runtime spec_version bumped 438 → 439 (and hydradx-runtime crate to 439.0.0).

[github-actions]

Crate versions that have been updated:

• runtime-integration-tests: v1.107.0 -> v1.107.1
• hydradx-runtime: v438.0.0 -> v439.0.0

Runtime version has been increased.

[Copilot]

Pull request overview

This PR fixes NTT over-limit mint behavior in the EVM currencies precompile so that exceeding the per-period mint budget triggers the circuit breaker’s reserve-and-lockdown mechanism (matching the XCM deposit path) instead of reverting and leaving funds stranded on the source chain.

Changes:

• Removed the redundant IssuanceIncreaseFuse::can_mint pre-check from the NTT mint precompile entrypoint so the actual PostDeposit hook can reserve excess and lock down the asset.
• Updated NTT precompile integration tests to assert successful mint + correct reserved/free balances and lockdown state, rather than expecting a MintLimitReached() revert.
• Reframed the burn test to validate the fuse’s net-issuance accounting within a period.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
runtime/hydradx/src/evm/precompiles/multicurrency.rs	Drops the pre-check that caused over-limit mints to revert before the circuit breaker could reserve/lock down.
integration-tests/src/evm.rs	Updates currency_precompile_ntt tests to cover reserve + lockdown semantics and net-budget behavior.

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[github-actions]

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