ci: add Node 26 to test matrix

[ricellis]

PR summary

Add new Node.js 26 to test matrix

Fixes: part of s1314

Note: An existing issue is required before opening a PR.

PR Checklist

Please make sure that your PR fulfills the following requirements:

• The commit message follows the
  Angular Commit Message Guidelines.
• Tests for the changes have been added (for bug fixes / features) - N/A
• Docs have been added / updated (for bug fixes / features) - N/A

PR Type

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• New tests
• Build/CI related changes
• Documentation content changes
• Other (please describe)

What is the current behavior?

Tests against Node 22, 24, 25

What is the new behavior?

Tests against Node 22, 24, 26

Does this PR introduce a breaking change?

• Yes
• No

Other information