Update GitHub Actions to latest versions and validate workflow triggers

[Copilot]

Updates all GitHub Actions to their latest versions and ensures workflows build on pushes/PRs to main, including dependabot PRs.

Changes

• Updated actions/checkout: v4 → v6 across all workflows (ci.yml, validate-workflows.yml, build-packages-v1.yml)
• Verified trigger configuration: All build workflows correctly trigger on push and pull_request to main branch, which automatically includes dependabot PRs

Affected Workflows

• ci.yml: Builds project via npm run build
• build-packages-v1.yml: Builds packages-v1 via npm run build
• validate-workflows.yml: Validates workflow syntax and checks for outdated actions

Note: actions/setup-node@v4 and actions/upload-artifact@v4 are already at latest versions.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Update GitHub Actions</issue_title>
<issue_description>- Update all action files in this repo with the latest GitHub Action versions

• Validate all action files in this repo build the source on pushes to main or PRs to main including dependabot PRs. </issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Update GitHub Actions #30

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