fix: use bash shebang for pipefail support

Ubuntu's default /bin/sh is dash, which doesn't support pipefail.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: dylanjha

install.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env bash
 set -euo pipefail
 
 # Detect platform

scripts/publish.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env bash
 set -euo pipefail
 
 # Publish @mux/cli and platform packages to npm.