ci: add install script workflow (#7159)

* ci: add install script workflow

Add GitHub Actions workflow to test install.sh script.

This prevents regressions like the one reported in issue #7133 where
changes to the install script broke the recommended installation method.

The workflow includes:
- shellcheck for script linting (temporarily excludes SC3045)
- Integration test using curl piped to sh as documented on starship.rs

Signed-off-by: cappyzawa <cappyzawa@gmail.com>

* fixup! ci: add install script workflow

Signed-off-by: cappyzawa <cappyzawa@gmail.com>

* fixup! ci: add install script workflow

Signed-off-by: cappyzawa <cappyzawa@gmail.com>

* ci: add shfmt check and format install scripts

Add shfmt job to install-script workflow for consistent shell script
formatting. Apply shfmt to all scripts under install/ directory.

Signed-off-by: cappyzawa <cappyzawa@gmail.com>

---------

Signed-off-by: cappyzawa <cappyzawa@gmail.com>

install/macos_packages/build_component_package.sh

@@ -9,45 +9,45 @@ set -euo pipefail
 # it is being run from within a starship repository if $1 is not provided.
 
 usage() {
-    echo "Builds a component package for macOS."
-    echo "Assumes that the following items already exist:"
-    echo "    - A starship binary which has already been notarized"
-    echo "    - Documentation created by \`npm run build\`, usually in a dist"
-    echo "      directory at <repo>/docs/.vitepress/dist"
-    echo "Usage: $0 <path-to-starship-binary> <path-to-dist-directory>"
+	echo "Builds a component package for macOS."
+	echo "Assumes that the following items already exist:"
+	echo "    - A starship binary which has already been notarized"
+	echo "    - Documentation created by \`npm run build\`, usually in a dist"
+	echo "      directory at <repo>/docs/.vitepress/dist"
+	echo "Usage: $0 <path-to-starship-binary> <path-to-dist-directory>"
 }
 
 script_dir="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" &>/dev/null && pwd)"
 source "$script_dir/common.sh"
 
 cleanup_server() {
-    if [[ -n "${server_pid-}" ]]; then
-        echo "Killing HTTP server ($server_pid) to clean up."
-        kill "$server_pid"
-        rm "x86_64-apple-darwin-simple-http-server"
-    else
-        echo "No server found, exiting normally."
-    fi
+	if [[ -n "${server_pid-}" ]]; then
+		echo "Killing HTTP server ($server_pid) to clean up."
+		kill "$server_pid"
+		rm "x86_64-apple-darwin-simple-http-server"
+	else
+		echo "No server found, exiting normally."
+	fi
 }
 
 if [[ "$OSTYPE" != 'darwin'* ]]; then
-    error "This script only works on MacOS"
+	error "This script only works on MacOS"
 fi
 
 if [[ "${2-undefined}" = "undefined" ]]; then
-    usage
-    exit 1
+	usage
+	exit 1
 fi
 
 starship_program_file="$1"
 starship_documentation_dir="$2"
 
 if [ ! -f "$starship_program_file" ]; then
-    error "Could not find starship binary at $starship_program_file"
+	error "Could not find starship binary at $starship_program_file"
 fi
 
 if [ ! -d "$starship_documentation_dir" ]; then
-    error "Could not find starship documentation at $starship_documentation_dir"
+	error "Could not find starship documentation at $starship_documentation_dir"
 fi
 
 pkgdir="$(mktemp -d)"