fix(ci): correct matrix strategy and bump action versions to v4

[Copilot]

The CI workflow had a broken matrix strategy — node-version was set to a scalar string instead of an array, and setup-node hardcoded the version rather than referencing ${{ matrix.node-version }}, making the matrix entirely ineffective.

Changes

• Matrix format: node-version: '24.13.0' → node-version: ['24.13.0']
• Matrix variable usage: node-version: '24.13.0' → node-version: ${{ matrix.node-version }} in the setup-node step
• Action versions: actions/checkout@v3 + actions/setup-node@v3 → @v4, consistent with npm-publish.yml

# Before
strategy:
  matrix:
    node-version: '24.13.0'   # scalar, not an array
...
      - uses: actions/checkout@v3
        uses: actions/setup-node@v3
        with:
          node-version: '24.13.0'  # ignores matrix entirely

# After
strategy:
  matrix:
    node-version: ['24.13.0']
...
      - uses: actions/checkout@v4
        uses: actions/setup-node@v4
        with:
          node-version: ${{ matrix.node-version }}

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