fix(gov): bound EndBlock vote tally work

[codchen]

Describe your changes and provide context

Governance proposal finalization previously iterated and deleted every stored vote in one EndBlock, allowing a proposal with many zero-power voters to concentrate unbounded work in its expiry block.

This change:

• shares a 1,000 vote-record budget across tallying and archived-vote cleanup in each EndBlock
• persists tally results, total voting power, tally parameters, a bonded-validator snapshot, and a vote cursor between blocks
• moves processed votes into round-specific archives and cleans those archives incrementally
• rejects new votes after incremental tallying begins
• isolates expedited and converted regular tally rounds
• includes both archived and pending votes when exporting an unfinished tally
• documents the new governance state and adds multi-block regression coverage

Proposal execution, deposit handling, hooks, and final events remain deferred until every vote has been processed.

Testing performed to validate your change

• go test ./sei-cosmos/x/gov/... -count=1
• go test -race ./sei-cosmos/x/gov ./sei-cosmos/x/gov/keeper -count=1
• go vet ./sei-cosmos/x/gov/...
• make fmtcheck with golangci-lint v2.8.0 rebuilt for Go 1.25
• golangci-lint v2.8.0 scoped to ./sei-cosmos/x/gov/... — 0 issues

[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	Aug 25, 2026, 5:14 AM

[codecov]

Codecov Report

❌ Patch coverage is 91.18943% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.04%. Comparing base (0997c3b) to head (7c3f7c7).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
sei-cosmos/x/gov/keeper/tally.go	91.05%	10 Missing and 7 partials ⚠️
sei-cosmos/x/gov/simulation/decoder.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4000      +/-   ##
==========================================
- Coverage   59.10%   58.04%   -1.07%     
==========================================
  Files        2305     2206      -99     
  Lines      197038   185640   -11398     
==========================================
- Hits       116453   107746    -8707     
+ Misses      69815    68058    -1757     
+ Partials    10770     9836     -934     

Flag	Coverage Δ
sei-chain-pr	60.00% <91.18%> (?)
sei-db	69.80% <ø> (-0.22%)	⬇️
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-cosmos/x/gov/abci.go	95.23% <100.00%> (+0.30%)	⬆️
sei-cosmos/x/gov/genesis.go	88.00% <100.00%> (+0.76%)	⬆️
sei-cosmos/x/gov/keeper/vote.go	92.85% <100.00%> (+0.85%)	⬆️
sei-cosmos/x/gov/types/keys.go	93.33% <100.00%> (+1.66%)	⬆️
sei-cosmos/x/gov/simulation/decoder.go	3.22% <0.00%> (-0.23%)	⬇️
sei-cosmos/x/gov/keeper/tally.go	91.13% <91.05%> (-5.65%)	⬇️

... and 101 files with indirect coverage changes

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