[epic] Add Full ABCI++ Support to Nibiru (internal/cosmos-sdk)

[matthiasmatt]

[epic] Add Full ABCI++ Support to Nibiru’s Forked Cosmos-SDK

This ticket now covers adding full ABCI++ support to Nibiru’s forked internal/cosmos-sdk, including all ABCI++ request and response types and the full FinalizeBlock + proposal-flow execution lifecycle. The work enables production use of the new ABCI methods without migrating to higher Cosmos-SDK versions, and without inheriting unrelated breaking changes from upstream.

The implementation affects only:

• internal/cosmos-sdk (baseapp, ABCI server/client logic, block lifecycle code)
• nibiru/app integration points

No CometBFT update is required. Consensus remains independent of the execution-layer work performed here.

Goals

• Support all ABCI++ methods:

  • PrepareProposal
  • ProcessProposal
  • FinalizeBlock (replacing BeginBlock / EndBlock)
  • ExtendVote
  • VerifyVoteExtension

• Align baseapp’s internal execution model with ABCI++ semantics
  (state transitions, intermediate state handling, event emission changes)

• Support downstream features such as:

  • improved pending-transaction management
  • better handling of tx interactions in the mempool
  • future parallel / optimistic execution paths

• Backport only the ABCI++ logic required for stable production use
  (not migrating to full SDK v0.50+)

Migration Path (to be filled in)

• [TODO]

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Ticket Changelog

• 2025-12-03 Pivot issue to instead involve updating CometBFT and the baseapp in isolation to Nibiru's forked cosmos-sdk dependency.
• 2025-05-14 Ticket creation: feat: migrate to cosmos-sdk v0.50

[DEPRECATED] Migration Guide for Cosmos-SDK v0.50

This section is no longer the target of the ticket.
The original plan to migrate the entire codebase toward SDK v0.50 has been superseded by a narrower, more maintainable approach: selectively backporting ABCI++ into Nibiru’s forked SDK instead of synchronizing with upstream’s broader breaking changes.

• migrate math feat: update dec and int to use cosmossdk.io/math #1872
• Guide on updating CometBFT for SDK v0.50
• Guide on updating cosmos-sdk/baseapp for SDK v0.50
• Config files
• Protobuf fix: remove all stringer for proto types #1874
• SimApp, packages, modules, tooling

[k-yang]

Need to fix linter errors and unit tests on the branch
Need to add upgrade handler

[k-yang]

CI tests are still failing, need to investigate why