autobahn parsing fixes (CON-311)

[pompon0]

giga p2p connection Request/Response types ad-hoc parsing was vulnerable to nil dereference.

[cursor]

PR Summary

Medium Risk
Touches consensus-related P2P ingest paths, but changes are mostly structural validation with round-trip tests and should reduce crash risk from hostile wire data.

Overview
Centralizes giga P2P wire handling behind typed protoutils.Conv helpers in types.go, and routes availability/data streaming RPCs (avail.go, data.go) through those encoders/decoders instead of reading protobuf fields directly.

Incoming messages now use DecodeReq-style validation on nested signed votes/proposals and QC payloads, so malformed or partially empty peer messages return errors instead of risking nil dereferences during ad-hoc parsing. GetBlock responses are modeled as an optional block (GetBlockRespConv + utils.Option) rather than checking resp.Block == nil after a partial decode.

Adds types_test.go round-trip tests for the new converters; fixes a mislabeled AppVote decode error string on the client app-votes stream.

^{Reviewed by Cursor Bugbot for commit 017e4e3. Bugbot is set up for automated code reviews on this repo. Configure here.}

[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	Jun 3, 2026, 4:17 PM

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The latest Buf updates on your PR. Results from workflow Buf / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Jun 3, 2026, 3:24 PM

[codecov]

Codecov Report

❌ Patch coverage is 85.92593% with 19 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.29%. Comparing base (2151ba0) to head (017e4e3).

Files with missing lines	Patch %	Lines
sei-tendermint/internal/p2p/giga/avail.go	58.62%	5 Missing and 7 partials ⚠️
sei-tendermint/internal/p2p/giga/data.go	68.18%	3 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3541      +/-   ##
==========================================
- Coverage   59.12%   58.29%   -0.83%     
==========================================
  Files        2213     2141      -72     
  Lines      182814   174520    -8294     
==========================================
- Hits       108096   101745    -6351     
+ Misses      64993    63727    -1266     
+ Partials     9725     9048     -677     

Flag	Coverage Δ
sei-chain-pr	68.76% <85.92%> (?)
sei-db	70.41% <ø> (ø)
sei-db-state-db	?

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

Files with missing lines	Coverage Δ
sei-tendermint/internal/p2p/giga/types.go	100.00% <100.00%> (ø)
sei-tendermint/internal/p2p/giga/data.go	67.34% <68.18%> (-1.20%)	⬇️
sei-tendermint/internal/p2p/giga/avail.go	58.82% <58.62%> (-1.05%)	⬇️

... and 73 files with indirect coverage changes

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