Optimize conflict-heavy EVM transfer execution

[codchen]

Summary

• Reuses the preprocessed derived sender during EVM DeliverTx association to avoid repeating signature recovery work.
• Reuses an empty cast auth account for EVM association when it is safe, preserving account number/sequence and avoiding extra account-number churn.
• Skips direct-cast self migration when the cast address and derived Sei address are the same.
• Detects large simple EVM transfer blocks that all target the same recipient and routes them through sequential execution instead of OCC retry churn. This applies to both the regular V2 path and the Giga path.

This is split out from #3376 so the behavior changes can be reviewed separately from logging and stress tooling.

Test Plan

• go test ./app ./utils/helpers ./app/ante ./x/evm/ante ./x/evm/types

[github-actions]

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	May 7, 2026, 4:54 AM

[codecov]

Codecov Report

❌ Patch coverage is 57.50000% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.03%. Comparing base (ab54587) to head (7623f7b).

Files with missing lines	Patch %	Lines
app/app.go	50.00%	9 Missing and 2 partials ⚠️
app/ante/evm_delivertx.go	45.45%	3 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3405      +/-   ##
==========================================
- Coverage   59.03%   59.03%   -0.01%     
==========================================
  Files        2105     2105              
  Lines      173300   173339      +39     
==========================================
+ Hits       102312   102334      +22     
- Misses      62104    62116      +12     
- Partials     8884     8889       +5     

Flag	Coverage Δ
sei-chain-pr	49.34% <57.50%> (?)
sei-db	70.41% <ø> (ø)

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

Files with missing lines	Coverage Δ
utils/helpers/associate.go	72.72% <100.00%> (+7.34%)	⬆️
app/ante/evm_delivertx.go	67.74% <45.45%> (-4.81%)	⬇️
app/app.go	69.39% <50.00%> (-0.30%)	⬇️

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