Update v6.7 changelog in prep to cut rc3

[alexander-sei]

Adds the release/v6.7 entries merged since the rc2 changelog (#4293), in prep to cut v6.7.0-rc3:

• #4348 — fix(seidb): report only the current migration boundary on the snapshot gauge
• #4347 — fix(flatkv): keep 10 old checkpoints instead of mirroring memIAVL's count
• #4334 — Fail dynamic-gas precompile out-of-gas as an EVM out-of-gas call
• #4315 — Pin the Go builder image per architecture in build-static.sh
• #4313 — fix(memiavl): hold a snapshot reference for an iterator's lifetime
• #4295 — rc2 version bump
• #4294 — rc2 changelog backport

Also returns ## v6.7 to the format used through v6.6: the version heading, sei-chain, and the generated PR list. The hand-written ### Improvements and ### Upgrade guide sections are removed; every PR they described is already a line in the generated list.

Regenerated with ./scripts/generate-changelog.sh release/v6.6 release/v6.7; only the ## v6.7 section changes. Docs-only; no code change.

Backport note: the #4347 backport already added its own line to the top of the ## v6.7 list on release/v6.7, so the backport release/v6.7 cherry-pick of this PR conflicts at that one spot (simulated with git merge-tree). Resolve it by taking this PR's side: its seven lines already include #4347.

[github-actions]

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Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Sep 25, 2026, 8:27 PM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 66.43%. Comparing base (3a61e67) to head (9e71338).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4335      +/-   ##
==========================================
- Coverage   67.55%   66.43%   -1.13%     
==========================================
  Files        2162     2041     -121     
  Lines      167529   155445   -12084     
==========================================
- Hits       113182   103273    -9909     
+ Misses      54338    52163    -2175     
  Partials        9        9              

Flag	Coverage Δ
sei-db	74.50% <ø> (ø)
sei-db-state-db	?

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[cursor]

PR Summary

Low Risk
Only CHANGELOG.md is edited; release notes formatting with no code or configuration impact.

Overview
Prepares v6.7.0-rc3 by regenerating the ## v6.7 block in CHANGELOG.md with ./scripts/generate-changelog.sh release/v6.6 release/v6.7.

The section now matches the v6.6-style layout (sei-chain plus an auto-generated PR list). Seven entries are prepended for work merged on release/v6.7 since the rc2 changelog (#4294), including seidb snapshot-gauge reporting, flatkv checkpoint retention, dynamic-gas precompile OOG behavior, memiavl iterator snapshot refs, and the rc2 version/changelog bumps.

The hand-written ### Improvements and ### Upgrade guide subsections are removed; those topics remain discoverable as individual lines in the generated list. Documentation only—no runtime or build behavior changes.

^{Reviewed by Cursor Bugbot for commit 9e71338. Bugbot is set up for automated code reviews on this repo. Configure here.}

[seidroid]

This PR only changes the changelog. The new rc3 entries match the PR list and follow the v6.6 format. However, it deletes the v6.7 upgrade guide, which holds operator migration steps that appear nowhere else in the repo's docs.

Findings: 0 blocking | 1 non-blocking | 1 posted inline

Blockers

• None at the file/PR level.

Non-blocking

• None at the file/PR level.
• 1 suggestion(s)/nit(s) flagged inline on specific lines.

[seidroid]

[suggestion] The description says every PR this ### Upgrade guide described is already a line in the generated list. That doesn't hold. The generated PR titles keep none of the guidance operators need to act on:

• The WebSocket frame limit default drops from 10 MiB to 5 MiB. Operators who need the old limit must set max_request_body_bytes = 10485760.
• ABCI/gRPC pagination is now capped by default, with [query] trusted-cidrs and disable-limits as ways around the caps.
• The legacy sei_* RPC methods are removed, and the guide listed their replacements.
• Historical IBC, transfer and feegrant data must now be served by v6.6 freeze nodes.

The IBC core, IBC query and capability-removal items had no PR number at all. Nothing else in the repo's markdown carries this guidance. Without it, clients sending 5–10 MiB WebSocket frames and indexers that page with large limits can break without warning after the upgrade. Keep this section, or move it to an upgrade/migration doc and link to it from ## v6.7. Codex raised the same point.