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: c1541fc

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 94.48%. Comparing base (9839a50) to head (c1541fc).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2990   +/-   ##
=======================================
  Coverage   94.48%   94.48%           
=======================================
  Files          45       45           
  Lines        7900     7900           
  Branches      708      708           
=======================================
  Hits         7464     7464           
  Misses        428      428           
  Partials        8        8           

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[WilliamBergamin]

This seems to be an issue with dependencies to mocha