Reject native multisig transaction simulation

[masih]

Reject multisig keys and signature data during gas simulation while
leaving normal transaction execution and single-signature simulation unchanged.

Part of SIP-3

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.25%. Comparing base (45bad90) to head (389a16a).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4037      +/-   ##
==========================================
- Coverage   61.24%   60.25%   -1.00%     
==========================================
  Files        2153     2054      -99     
  Lines      188393   176718   -11675     
==========================================
- Hits       115387   106477    -8910     
+ Misses      62274    60477    -1797     
+ Partials    10732     9764     -968     

Flag	Coverage Δ
sei-chain-pr	77.39% <100.00%> (?)
sei-db	69.80% <ø> (ø)
sei-db-state-db	?

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Files with missing lines	Coverage Δ
sei-cosmos/x/auth/ante/sigverify.go	73.37% <100.00%> (+0.94%)	⬆️

... and 99 files with indirect coverage changes

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[github-actions]

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Aug 27, 2026, 5:30 PM