Maintenance - upgrade Meteor to 3.4 in testapp

[jankapunkt]

Upgrades npm deps, ci and Meteor to 3.4

[Copilot]

Pull request overview

This PR upgrades the testapp3 Meteor test application to Meteor 3.4, refreshes related npm dev dependencies, and updates CI to run against newer Node/Meteor versions.

Changes:

• Bump testapp3 Meteor release to METEOR@3.4 and update .meteor/packages / .meteor/versions accordingly.
• Update testapp3 npm dependencies/devDependencies (Babel runtime, nyc, chai, puppeteer, etc.).
• Update GitHub Actions workflow to use Node 22 and add Meteor 3.4 to the test matrix.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
testapp3/package.json	Updates npm dependency versions used by the Meteor 3 test app.
testapp3/.meteor/versions	Refreshes Meteor package versions for the Meteor 3.4 upgrade.
testapp3/.meteor/release	Pins the test app to METEOR@3.4.
testapp3/.meteor/packages	Updates pinned Meteor package versions (e.g., mongo, static-html, minifiers, typescript).
.github/workflows/testsuite.yml	Moves CI to Node 22 and expands Meteor 3 testing to include 3.4.

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[Copilot]

The meteorRelease matrix likely won’t actually control which Meteor version runs because the app is pinned to METEOR@3.4 in testapp3/.meteor/release and the meteor test-packages command isn’t passed --release ${{ matrix.meteorRelease }} (or equivalent). This can cause the 3.0.2 matrix entry to still run Meteor 3.4 (or fail due to release mismatch), reducing the value of the matrix. Consider invoking meteor --release ${{ matrix.meteorRelease }} test-packages ... or rewriting testapp3/.meteor/release per matrix entry before running tests.