Oxygen add-on for XSpec v3.4.2

[galtm]

This pull request creates the Oxygen add-on for XSpec v3.4.2, the release candidate.

(In the description, the phrasing is a little different from the draft XSpec v3.4 release notes only because this change description distinguishes between 3.4.1 and 3.4.2, whereas the v3.4 release notes don't.)

To do, in this order:

• Merge build(oxygen): add-on v3.4.2 xspec#2273 into master. That will create the v3.4.2.zip file.
• On the branch for this PR, run hugo locally and test installation of the add-on with local URL: http://localhost:1313/editors/oxygen/oxygen-addon.xml (To check that opening xspec.xpr in your own clone disables the add-on and enables its own framework, you have to sync your clone to master.)
• Merge this PR onto hugo branch.
• Uninstall add-on, and test re-installation with remote URL: https://xspec.io/editors/oxygen/oxygen-addon.xml

Cc: @cmarchand

[galtm]

I installed and tested the add-on with Oxygen XML Editor 28.0 build 2025112606. Ran tests for:

• XSLT (Run XSpec Test, XSLT Code Coverage, and the XProc-based transformation scenario)
• XQuery (Run XSpec Test and the XProc-based transformation scenario)
• Schematron via XQS
• Schematron via SchXslt

For the two XProc transformation scenarios, the bottom pane of messages indicated XML Calabash 3.x instead of XML Calabash 1.x.

The XSpec templates for tests for XQuery and Schematron looked fine.

[galtm]

• Uninstall add-on, and test re-installation with remote URL: https://xspec.io/editors/oxygen/oxygen-addon.xml

Done.