docs(changelog): point commit links at the rewritten history

[baseballyama]

Summary

main was rewritten from #233 onward to remove the Microsoft Excel UI dumps and screenshots that #297 deleted, so every commit since #233 has a new hash. This PR updates the 20 CHANGELOG lines (15 commits) that linked to the old hashes, so the links don't break once GitHub stops serving the unreachable commits.

Motivation

Follow-up to the history rewrite done after #297.

Changes

• CHANGELOG.md: each old commit hash is replaced with its rewritten one, both in the full-hash URLs and in the short-hash labels.

Testing

• Every new hash resolves to the commit with the same subject on main (checked with git cat-file -e / git log -1).

Breaking changes

None

Checklist

• I have read CLAUDE.md and followed the project's conventions.
• I have added or updated tests for the change. (Docs only.)
• I have added or updated documentation where user-visible behavior changed.
• If this is a breaking change, I have added a changeset / CHANGELOG entry and flagged it above. (Not breaking.)
• I have re-read my own diff and removed dead code, debug prints, and stale comments.
• If I used an LLM to draft this PR, I have verified each change myself, the PR represents real work that warrants a maintainer's review, and I am willing to defend each line in review.

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