perf(ProcessProposal): skip IsTxGasless in checkTotalBlockGas for non-gasless txs

[amir-deris]

Summary

checkTotalBlockGas previously called antedecorators.IsTxGasless unconditionally for every tx before doing EVM/Cosmos gas accounting. For typical MsgEVMTransaction txs, IsTxGasless always returned (false, nil) immediately via the default branch — but still paid the cost of a defer/recover frame and a message-type walk on every tx.

This PR mirrors the couldBeGaslessTransaction heuristic already used in DeliverTxWithResult and OCC paths:

1. Fast-path guard: IsEVMMessage is hoisted to the top of the loop (it was already called later for gas accounting). For confirmed single-message EVM txs (isEVM && evmErr == nil), IsTxGasless is skipped entirely — MsgEVMTransaction can never be gasless under the current rules.
2. Heuristic guard: for all other txs, couldBeGaslessTransaction is checked first. Only oracle vote and MsgAssociate txs proceed to the full keeper-backed IsTxGasless call.

Semantics are unchanged: txs for which IsTxGasless would have returned (false, nil) are now classified as non-gasless without the extra overhead.

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	May 5, 2026, 7:54 AM

[codecov]

Codecov Report

❌ Patch coverage is 46.15385% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.06%. Comparing base (cb91c34) to head (f386742).

Files with missing lines	Patch %	Lines
app/app.go	46.15%	5 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3380      +/-   ##
==========================================
- Coverage   59.07%   59.06%   -0.01%     
==========================================
  Files        2099     2098       -1     
  Lines      172970   172951      -19     
==========================================
- Hits       102183   102161      -22     
- Misses      61922    61931       +9     
+ Partials     8865     8859       -6     

Flag	Coverage Δ
sei-chain-pr	50.70% <46.15%> (?)
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
app/app.go	69.85% <46.15%> (+0.29%)	⬆️

... and 25 files with indirect coverage changes

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[codchen]

another optimization we can make is for this loop to run concurrently and add to total block gas as an atomic int. The only advantage of sequential is if the loop early returns, which is rare.

[amir-deris]

Thanks for feedback. Created a follow up ticket: https://linear.app/seilabs/issue/PLT-324/