feat: support libmusl detection

[bandogora]

Add LIBC and adjust_libc() + minor linting

Closes #243

[bandogora]

Have to adjust for static flag -s which doesn't have _libmusl prefix

[Copilot]

Pull request overview

Adds libc detection to the installer so it can download the correct release artifact on musl-based Linux distributions (e.g., Alpine), addressing issue #243.

Changes:

• Introduces LIBC detection and adjust_libc() to append _libmusl to Linux artifact names when needed.
• Updates archive name construction and logging to incorporate libc selection.
• Applies minor formatting/linting tweaks (blank lines, shellcheck directive adjustment).

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[Copilot]

LIBC detection unconditionally invokes ldd --version even on non-Linux platforms. With set -e, shells like dash may emit ldd: not found to stderr (and potentially abort) because the command-not-found error is produced by the shell and can bypass the 2>&1 redirection. Consider gating libc detection behind an OS check and is_command ldd (e.g., only detect on Linux; otherwise default to glibc/empty suffix) so macOS/Windows users don't see errors and the script stays portable.

Suggested change

	LIBC=$(ldd --version 2>&1 | grep -qi musl && printf 'libmusl' || printf 'glibc')
	# Detect libc variant only where applicable; default to glibc otherwise.
	if [ "$OS" = "linux" ] && command -v ldd >/dev/null 2>&1; then
	if ldd --version 2>&1 | grep -qi musl; then
	LIBC='libmusl'
	else
	LIBC='glibc'
	fi
	else
	LIBC='glibc'
	fi