fix(giga): match v2 correctness checks

[arajasek]

Describe your changes and provide context

This PR improves and cleans up the validation performed by the Giga executor before running a tx:

• Calls EvmStatelessChecks directly
• Moves all other validation into its own method
• Bumps nonce if and only if the nonce is correct, as per v2
  • Basically "if nonce is correct, it will get bumped, regardless of any other potential failures"
• Orders the various validation checks to match v2, so that in the edge-case where multiple things fail, we respect v2's behaviour
• Matches v2 panic recovery
  • Seq mode needs to trap panics
  • OCC mode needs to lower panics to the appropriate error code: ErrOCCAbort, ErrOutOfGas, or ErrPanic

Testing performed to validate your change

Bunch of new AI-generated tests. Will confirm it syncs mainnet shortly.

[arajasek]

This PR subsumes #3017. #3045, #3061

[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	Mar 13, 2026, 6:56 PM

[codecov]

Codecov Report

❌ Patch coverage is 38.17204% with 115 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.40%. Comparing base (bb2c5b3) to head (5f624e7).

Files with missing lines	Patch %	Lines
app/app.go	38.17%	102 Missing and 13 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3071      +/-   ##
==========================================
- Coverage   58.41%   58.40%   -0.01%     
==========================================
  Files        2081     2081              
  Lines      171790   171918     +128     
==========================================
+ Hits       100352   100410      +58     
- Misses      62504    62572      +68     
- Partials     8934     8936       +2     

Flag	Coverage Δ
sei-chain-pr	55.15% <38.17%> (?)
sei-db	70.41% <ø> (-0.22%)	⬇️

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

Files with missing lines	Coverage Δ
app/app.go	67.33% <38.17%> (-2.00%)	⬇️

... and 1 file with indirect coverage changes

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[masih]

We need to differentiate between panic types otherwise returning everything as ABCICode would be apphash breaking i think.

We have 2 off the top of my head: scheduler.Abort and sdk.ErrorOutOfGas. We would want to check for OOG error type here jsut to be on the safe side.

[masih]

Hmm @arajasek we don't return result or execErr out from this func.

I recommend changing the function signature and use named return types prefixed with _ and use those instead. That is far less error prone against future refactors too.