chore(ci): install actionlint from release binary

[Copilot]

Install actionlint from GitHub release binaries using the same pattern as zizmor, eliminating the Go toolchain dependency.

Changes

• copilot-setup-steps.yml: Replace go install with gh release download for actionlint
• actionlint.yml: Apply same installation method for consistency
• Remove "Add GOPATH to PATH" steps (no longer needed)

Pattern

- name: Install Actionlint
  env:
    TMP_DIR: ${{ runner.temp }}
    GH_TOKEN: ${{ github.token }}
  run: |
    set -euo pipefail
    tarball="$TMP_DIR/actionlint.tar.gz"
    gh release download --repo rhysd/actionlint --pattern "actionlint_*_linux_amd64.tar.gz" --output "$tarball"
    tar -xzf "$tarball" -C "$TMP_DIR"
    install -D "$TMP_DIR/actionlint" /usr/local/bin
    rm "$tarball" "$TMP_DIR/actionlint"

Downloads latest release automatically via wildcard pattern. Faster (~30-60s saved vs compilation) and consistent with existing zizmor installation.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/graphql
  • Triggering command: /usr/bin/gh gh release list --repo rhysd/actionlint --limit 3 (http block)
• https://api.github.com/repos/rhysd/actionlint/releases/latest
  • Triggering command: /usr/bin/curl curl -s REDACTED (http block)
  • Triggering command: /usr/bin/curl curl -sL REDACTED (http block)
  • Triggering command: /usr/bin/gh gh release view --repo rhysd/actionlint --json assets --jq .assets[].name (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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