Update v6.7 changelog in prep to cut v6.7.0

[alexander-sei]

Adds the release/v6.7 entries merged since the rc4 changelog (#4406), in prep to cut v6.7.0, the mainnet release (there is no rc5; the version bump is #4444):

• #4442 — fix(seidb): fix stale FlatKV migration gauges on snapshotting nodes
• #4439 — seidb: add changelog mode and --inspect-plan to speed up EVM digest
• #4416 — removal of the conflict markers the rc4 changelog backport left on release/v6.7
• #4415 — rc4 changelog backport
• #4407 — rc4 version bump

Regenerated with ./scripts/generate-changelog.sh release/v6.6 release/v6.7; only the ## v6.7 PR list changes, so the backport release/v6.7 cherry-pick applies cleanly (simulated with git merge-tree against origin/release/v6.7). Docs-only; no code change.

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	Oct 5, 2026, 8:28 AM

[seidroid]

Settled by the scouts (codex) without a review turn: every one of them read the diff, found nothing, and reported it inert -- comments, documentation or whitespace only, with no executable surface changed.

_{seidroid review · decision approve · settled by the scouts codex · no review turn ran}

Findings: 0 blocking | 0 non-blocking | 0 posted inline

[masih]

LGTM, but the PR title is inaccurate.

@alexander-sei we are going to cut v6.7 -- not anohter release candidate ;)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 54.98%. Comparing base (82c0cda) to head (39069b8).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4443      +/-   ##
==========================================
- Coverage   56.75%   54.98%   -1.77%     
==========================================
  Files        2126     2003     -123     
  Lines      166836   154474   -12362     
==========================================
- Hits        94691    84944    -9747     
+ Misses      72140    69525    -2615     
  Partials        5        5              

Flag	Coverage Δ
sei-db	74.81% <ø> (ø)
sei-db-state-db	?

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[seidroid]

Successfully created backport PR for release/v6.7:

• Backport release/v6.7: Update v6.7 changelog in prep to cut v6.7.0 #4445