Use DBImpl for giga mock balance validation

[codchen]

Summary

Routes giga executor balance validation through the giga EVM DBImpl so mock_balances builds can top off accounts through the existing ensureSufficientBalance hook before validation rejects the tx.

Root Cause

validateGigaEVMTx was checking balances with GigaEvmKeeper.GetBalance, bypassing DBImpl. The actual debit path already used DBImpl, so mock balance support worked for execution but not for manual validation prechecks.

Changes

• Create the giga DBImpl before validation and pass it into validateGigaEVMTx.
• Add a DBImpl.EnsureSufficientBalance wrapper for validation-time affordability checks.
• Use DB-backed GetBalance during validation, including the unassociated-address balance case.
• Add a mock_balances regression test covering a large unfunded giga transfer.

Validation

• go test ./giga/deps/xevm/state -run TestSubBalance -count=1
• go test ./giga/tests -run TestGigaValidation_InsufficientBalance -count=1
• go test -tags mock_balances ./giga/tests -run TestGigaMockBalancesValidationUsesDBImpl -count=1

[github-actions]

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Jul 13, 2026, 4:02 PM

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.00%. Comparing base (79b12b9) to head (d11034c).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
giga/deps/xevm/state/balance.go	50.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3750      +/-   ##
==========================================
- Coverage   59.91%   59.00%   -0.92%     
==========================================
  Files        2288     2201      -87     
  Lines      189782   179957    -9825     
==========================================
- Hits       113706   106176    -7530     
+ Misses      65942    64448    -1494     
+ Partials    10134     9333     -801     

Flag	Coverage Δ
sei-chain-pr	61.29% <85.71%> (?)
sei-db	70.41% <ø> (ø)
sei-db-state-db	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
app/app.go	71.20% <100.00%> (+0.03%)	⬆️
giga/deps/xevm/state/balance.go	60.21% <50.00%> (-0.46%)	⬇️

... and 87 files with indirect coverage changes

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