ci: add Node 26 to the test matrix

[zimeg]

Summary

This pull request adds Node 26 to the Bolt for JavaScript CI test matrix.

• Adds 26.x to the node-version matrix in .github/workflows/ci-build.yml.

Split out from #2989 so the Dependabot/config changes can land independently if the Node 26 test leg needs work.

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 8018f79

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.33%. Comparing base (e2b90aa) to head (8018f79).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2990   +/-   ##
=======================================
  Coverage   94.33%   94.33%           
=======================================
  Files          43       43           
  Lines        7360     7360           
  Branches      679      679           
=======================================
  Hits         6943     6943           
  Misses        409      409           
  Partials        8        8           

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[WilliamBergamin]

This seems to be an issue with dependencies to mocha