feat(#616): add Node 26 to CI matrices

[RomiC]

Closes #616

Changes

• Added Node 26 to the test matrix in both npm-test.yml and npm-publish.yml
• Added "overrides": { "yargs": "^18.0.0" } to package.json to unblock c8 on Node 26

Context

c8 bundles yargs@17.7.2 which has "type": "module" but its ./yargs entrypoint uses require(). Node 26's now-stable require()-of-ESM feature properly loads it as ESM, causing require() inside the file to fail. Overriding yargs to ^18.0.0 resolves this.

The upstream fix is tracked in bcoe/c8#578. Once it ships, the override can be removed — tracked in #643.

Verified on Node 26

All scripts pass clean on Node 26:

• npm run lint ✅
• npm test ✅
• npm run test:coverage ✅
• npm run build ✅
• npm run smoke ✅

[coveralls]

coverage: 100.0%. remained the same — feat/616-node26-ci into master

[Copilot]

Pull request overview

Adds Node.js 26 coverage to the project’s GitHub Actions CI matrices and introduces an npm overrides entry to keep the Node 26 test/coverage toolchain working (via forcing yargs to a Node-26-compatible version for c8’s dependency tree).

Changes:

• Expanded the Node version matrix to include Node 26 in both test and publish workflows.
• Added an npm overrides rule for yargs (and updated the lockfile accordingly) to unblock c8 on Node 26.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated no comments.

File	Description
package.json	Adds overrides to force yargs v18 to keep c8 working on Node 26.
package-lock.json	Updates resolved dependency graph to reflect the yargs override (including transitive updates).
.github/workflows/npm-test.yml	Adds Node 26 to the CI test matrix.
.github/workflows/npm-publish.yml	Adds Node 26 to the release build/test matrix prior to publish.

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