Backport release/v6.6: Generate v6.6 CHANGELOG

[seidroid]

Backport of #3634 to release/v6.6.

[cursor]

PR Summary

Low Risk
Documentation-only changelog edit with no code or configuration changes.

Overview
Adds a new ## v6.6 section at the top of CHANGELOG.md (above v6.5), listing merged sei-chain PRs for the v6.6 release line as linked bullet entries.

This is a release-notes / backport update only (backport of #3634 to release/v6.6); it does not change application, consensus, or RPC behavior.

^{Reviewed by Cursor Bugbot for commit a3ec81a. 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 24, 2026, 10:51 AM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.01%. Comparing base (6b3812e) to head (a3ec81a).
⚠️ Report is 1 commits behind head on release/v6.6.

Additional details and impacted files

@@               Coverage Diff                @@
##           release/v6.6    #3635      +/-   ##
================================================
- Coverage         58.89%   58.01%   -0.89%     
================================================
  Files              2225     2151      -74     
  Lines            183480   174933    -8547     
================================================
- Hits             108057   101482    -6575     
+ Misses            65714    64442    -1272     
+ Partials           9709     9009     -700     

Flag	Coverage Δ
sei-db	70.41% <ø> (ø)
sei-db-state-db	?

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see 74 files with indirect coverage changes

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