fix(x/auth/tx): keep nested multisig ModeInfos in GetSigningTxData

[kriss39]

Description

adaptModeInfo (used by wrapper.GetSigningTxData to convert the gogoproto AuthInfo into the x/tx TxData) allocates the modeInfos slice for a multisig ModeInfo but adapts every nested entry into a throwaway &txv1beta1.ModeInfo{} and never stores it:

modeInfos := make([]*txv1beta1.ModeInfo, len(multiModeInfos))
for _, modeInfo := range multiModeInfos {
    adaptModeInfo(modeInfo, &txv1beta1.ModeInfo{})
}

The converted ModeInfo_Multi therefore carries a slice of nil pointers instead of the sub-signer mode infos. The current sign mode handlers do not read this field (DIRECT uses the raw AuthInfoBytes), so this has been latent since #15910, but any handler or downstream consumer that inspects TxData.AuthInfo.SignerInfos[i].ModeInfo.GetMulti().ModeInfos gets nil entries. Same function as the recent nil Multi/Bitarray fix in #26571.

Changes

• Store each converted entry in modeInfos[i].
• Regression test TestGetSigningTxData_MultisigModeInfos: a 2-of-2 multisig signature with a DIRECT and a LEGACY_AMINO_JSON sub-signer; asserts both nested mode infos are present and carry the right modes. Fails on main (Expected value not to be nil).

[greptile-apps]

PR author is not in the allowed authors list.

[dianab-cl]

Please Sign the commits

[kriss39]

Done — replaced the commit with a signed one (ce7b429, same content), now shows as Verified.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.99%. Comparing base (8f265eb) to head (ce7b429).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #26815      +/-   ##
==========================================
+ Coverage   64.97%   64.99%   +0.01%     
==========================================
  Files         785      785              
  Lines       55413    55414       +1     
==========================================
+ Hits        36007    36016       +9     
+ Misses      19406    19398       -8     

Files with missing lines	Coverage Δ
x/auth/tx/adapter.go	98.87% <100.00%> (+0.01%)	⬆️

... and 6 files with indirect coverage changes

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