Reduce SS changelog retention to use the async buffer size

[yzang2019]

Describe your changes and provide context

This PR reduce the changelog retention for SS to a min value of 1000 entries (1000 blocks), and max up to the SS async write buffer size.

Testing performed to validate your change

[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	Feb 22, 2026, 4:22 AM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 63.42%. Comparing base (f4b318c) to head (c594bff).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2954       +/-   ##
===========================================
+ Coverage   57.82%   63.42%    +5.59%     
===========================================
  Files        2110       10     -2100     
  Lines      174122     1438   -172684     
===========================================
- Hits       100681      912    -99769     
+ Misses      64464      413    -64051     
+ Partials     8977      113     -8864     

Flag	Coverage Δ
sei-chain	61.06% <100.00%> (+3.26%)	⬆️
sei-db	68.49% <100.00%> (+0.06%)	⬆️

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

Files with missing lines	Coverage Δ
sei-db/db_engine/pebbledb/mvcc/db.go	60.13% <100.00%> (-3.79%)	⬇️
sei-db/db_engine/rocksdb/mvcc/db.go	57.48% <100.00%> (+0.17%)	⬆️

... and 2100 files with indirect coverage changes

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[seidroid]

Created backport PR for release/v6.3:

• Backport release/v6.3: Reduce SS changelog retention to use the async buffer size #2955 with remaining conflicts!

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin backport-2954-to-release/v6.3
git worktree add --checkout .worktree/backport-2954-to-release/v6.3 backport-2954-to-release/v6.3
cd .worktree/backport-2954-to-release/v6.3
git reset --hard HEAD^
git cherry-pick -x 3f0be7cc0b1850fd59325428df67415fa57b9a14
git push --force-with-lease