persist: add CRC32-C integrity check and seq validation to A/B files

[wen-coding]

Summary

• Add a crc32 field to PersistedWrapper proto covering both seq and data (CRC32-C Castagnoli, matching sei-tendermint/internal/libs/wal).
• On write, compute and store the checksum. On load, reject files with missing/zero seq or missing/mismatched crc32 as ErrCorrupt.
• This catches silent truncation and bit-rot that proto.Unmarshal alone would miss, since trailing optional fields can be silently lost.

Changes:

• autobahn.proto: new optional uint32 crc32 = 3 on PersistedWrapper
• persist.go: wrapperChecksum(seq, data) helper using CRC32-C over [8-byte LE seq || data]; validation in loadWrapped; checksum set in Persist
• persist_test.go: tests for CRC32 mismatch (data corruption), CRC32 mismatch (seq corruption), missing CRC32, missing seq, zero seq, and CRC32 round-trip verification

Test plan

• All autobahn tests pass (avail, consensus, persist, data, types)
• Race detector clean
• go vet clean

Made with Cursor

[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	Mar 21, 2026, 3:30 AM

[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	Mar 20, 2026, 11:33 PM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.68%. Comparing base (f6b04aa) to head (b740a7f).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3105   +/-   ##
=======================================
  Coverage   58.68%   58.68%           
=======================================
  Files        2096     2096           
  Lines      173248   173261   +13     
=======================================
+ Hits       101667   101680   +13     
  Misses      62541    62541           
  Partials     9040     9040           

Flag	Coverage Δ
sei-chain-pr	76.01% <100.00%> (?)
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
...int/internal/autobahn/consensus/persist/persist.go	82.08% <100.00%> (+1.92%)	⬆️

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