Build Bullseye-compatible linux-arm prebuilds for Node 22 alpha releases

[Copilot]

The alpha package path for linux-arm was present, but the shipped binary was not compatible with Raspberry Pi OS Bullseye on 32-bit ARM. On affected systems this surfaced as pty.node failing to load from prebuilds/linux-arm.

• Build linux-arm against a Bullseye userspace

  • Move the linux-arm prebuild job from Ubuntu host cross-compilation to a Debian Bullseye linux/arm/v7 container.
  • Keep the existing artifact layout unchanged so published packages still resolve prebuilds/linux-arm/pty.node in the same location.

• Add a release guard for ARM glibc compatibility

  • Add a workflow check that inspects the built linux-arm binary and fails if it links against glibc newer than Bullseye supports.
  • This prevents publishing another ARM prebuild that installs successfully but cannot be loaded at runtime.

• Align documented platform support

  • Update the README architecture table to reflect the ARM Linux variants the release workflow now produces.

- name: Build linux-arm in Debian Bullseye container
  if: matrix.crossCompile && matrix.arch == 'arm'
  run: |
    docker run --rm \
      --platform linux/arm/v7 \
      -v "${{ github.workspace }}:/workspace" \
      -w /workspace \
      -e ARCH=${{ matrix.arch }} \
      -e npm_config_arch=${{ matrix.arch }} \
      node:22-bullseye sh -c "
        set -e
        apt-get update
        apt-get install -y python3 make g++
        npm ci
      "

• Fixes Alpha fails for - RPi 3 Model B+, Bullseye, arm (32-bit), node 22.23.2 #100