Backport release/v6.5: Fix pre-v6.5 debug trace tx decoding

[seidroid]

Backport of #3470 to release/v6.5.

[seidroid]

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin backport-3470-to-release/v6.5
git worktree add --checkout .worktree/backport-3470-to-release/v6.5 backport-3470-to-release/v6.5
cd .worktree/backport-3470-to-release/v6.5
git reset --hard HEAD^
git cherry-pick -x 5098e5b0e902f51d8966003f33aaa440fde9b0d5
git push --force-with-lease

[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 20, 2026, 9:41 PM

[codecov]

Codecov Report

❌ Patch coverage is 94.59459% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.32%. Comparing base (fbc0d93) to head (01d737e).

Files with missing lines	Patch %	Lines
evmrpc/trace_tx_decoder.go	87.50%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##           release/v6.5    #3478   +/-   ##
=============================================
  Coverage         58.31%   58.32%           
=============================================
  Files              2093     2094    +1     
  Lines            173231   173261   +30     
=============================================
+ Hits             101018   101050   +32     
+ Misses            63148    63147    -1     
+ Partials           9065     9064    -1     

Flag	Coverage Δ
sei-chain-pr	64.17% <94.59%> (?)
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
evmrpc/simulate.go	72.81% <100.00%> (+0.73%)	⬆️
sei-cosmos/x/auth/tx/config.go	93.10% <100.00%> (+0.51%)	⬆️
sei-cosmos/x/auth/tx/decoder.go	88.34% <100.00%> (+0.59%)	⬆️
sei-cosmos/x/upgrade/keeper/keeper.go	92.79% <100.00%> (+0.09%)	⬆️
evmrpc/trace_tx_decoder.go	87.50% <87.50%> (ø)

... and 1 file with indirect coverage changes

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[cursor]

PR Summary

Medium Risk
Changes transaction decoding behavior in evmrpc tracing/simulation paths based on upgrade height; incorrect height detection or decoder selection could break tracing or cause unexpected decode failures for some blocks. Core mempool/DeliverTx decoding remains strict, limiting impact.

Overview
Fixes debug_trace*/block replay failures on pre-v6.5 historical Cosmos SDK transactions by conditionally using a compatibility tx decoder that does not reject protobuf body “bloat” introduced by the v6.5 canonical-size check.

Adds UpgradeKeeper.IsUpgradeActiveAtHeight and exposes TxConfig.ProtoCodec() so evmrpc can select the strict vs compat decoder per block height; updates Backend transaction decoding in GetTransaction, BlockByNumber, StateAtTransaction, and replay logic accordingly. Includes new unit tests covering the compat decoder behavior and ensuring strict decoding still rejects bloated bodies at/after v6.5.

^{Reviewed by Cursor Bugbot for commit 01d737e. Bugbot is set up for automated code reviews on this repo. Configure here.}