Fix bogus signatures in light client attack evidence

[pdrobnjak]

Describe your changes and provide context

Addresses cometbft/cometbft#1749 by backporting cometbft/cometbft#1750, cometbft/cometbft#1808, and cometbft/cometbft#1858.

Testing performed to validate your change

[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	Oct 24, 2025, 1:42 PM

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 53.05%. Comparing base (a697f8e) to head (b57ad48).
⚠️ Report is 570 commits behind head on main.

Files with missing lines	Patch %	Lines
sei-tendermint/types/validator_set.go	0.00%	4 Missing ⚠️

❌ Your patch check has failed because the patch coverage (33.33%) is below the target coverage (70.00%). You can increase the patch coverage or adjust the target coverage.
❌ Your project check has failed because the head coverage (48.28%) is below the target coverage (60.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2499      +/-   ##
==========================================
- Coverage   53.06%   53.05%   -0.02%     
==========================================
  Files        1615     1615              
  Lines      135520   135524       +4     
==========================================
- Hits        71919    71901      -18     
- Misses      56963    56984      +21     
- Partials     6638     6639       +1     

Flag	Coverage Δ
sei-chain	27.86% <0.00%> (-0.02%)	⬇️
sei-cosmos	52.37% <ø> (-0.01%)	⬇️
sei-db	48.18% <ø> (+0.01%)	⬆️
sei-tendermint	59.08% <33.33%> (-0.03%)	⬇️
sei-wasmd	46.45% <ø> (+0.02%)	⬆️

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

Files with missing lines	Coverage Δ
sei-tendermint/internal/evidence/verify.go	75.00% <100.00%> (ø)
sei-tendermint/types/validator_set.go	89.29% <0.00%> (-0.83%)	⬇️

... and 21 files with indirect coverage changes

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[github-actions]

We truly appreciate your contribution and the time you’ve invested in this PR.
Before we can merge it, we’d love your help addressing the remaining feedback or sharing your perspective.
If we don’t hear back within 2 day(s), this PR will close automatically — but don’t worry, you can reopen it anytime when you’re ready to continue.