proto conversion defensive tests (CON-240)

[pompon0]

• I've updated ProtoConv test to check if Decode does not panic on malformed proto messages (with missing fields). Decode expects the argument to be non-nil, but its fields are not guaranteed to be non-nil. Slices representing repeated values are guaranteed to contain non-nil values though.
• fixed TimeoutQC logic to disallow empty QCs.

[github-actions]

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Apr 7, 2026, 6:09 PM

[codecov]

Codecov Report

❌ Patch coverage is 71.11111% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.85%. Comparing base (9218c01) to head (fdc362c).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
sei-tendermint/internal/protoutils/testonly.go	64.51%	7 Missing and 4 partials ⚠️
sei-tendermint/internal/autobahn/types/timeout.go	66.66%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3206      +/-   ##
==========================================
+ Coverage   58.77%   58.85%   +0.07%     
==========================================
  Files        2055     2055              
  Lines      168498   168531      +33     
==========================================
+ Hits        99039    99193     +154     
+ Misses      60708    60637      -71     
+ Partials     8751     8701      -50     

Flag	Coverage Δ
sei-chain-pr	80.96% <71.11%> (?)
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
sei-tendermint/internal/autobahn/types/block.go	83.62% <100.00%> (+17.24%)	⬆️
sei-tendermint/internal/autobahn/types/msg.go	81.63% <100.00%> (+8.16%)	⬆️
sei-tendermint/internal/autobahn/types/proposal.go	91.45% <100.00%> (+9.12%)	⬆️
sei-tendermint/internal/p2p/conv.go	88.52% <ø> (+9.83%)	⬆️
sei-tendermint/internal/autobahn/types/timeout.go	78.66% <66.66%> (+3.32%)	⬆️
sei-tendermint/internal/protoutils/testonly.go	59.52% <64.51%> (+14.06%)	⬆️

... and 16 files with indirect coverage changes

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