cli: Always use musl binary on Linux to fix segfault in prebuilt binary

[Copilot]

The prebuilt Linux binary is glibc-linked and compiled against the CI runner's glibc version. On systems with a different glibc it crashes with SIGSEGV. The musl binary is fully statically linked and works on any Linux system.

Changes

• install: Remove ldd-based musl detection. Always use the -musl artifact on Linux.

  # Before: only used musl binary on musl hosts
  if ldd --version 2>&1 | grep -q 'musl'; then libc='-musl'; fi
  
  # After: always use statically-linked musl binary on Linux
  if [ "$platform" = "linux" ]; then libc='-musl'; fi

• release.yml:

  • Replace deprecated/archived actions-rs/cargo@v1 with direct cargo build / cross build commands.
  • Add explicit cross: true/false per matrix target. x86_64-unknown-linux-musl now compiles natively with musl-tools (no Docker); aarch64 targets continue to use cross.

• test-install.yml:

  • Add linux-musl-on-glibc job: runs sh install on an Ubuntu (glibc) runner and verifies the binary executes — exactly the scenario from the reported segfault.
  • Add the workflow file itself to trigger paths.
  • Add top-level permissions: contents: read.