Fix install.sh OS/arch casing to match GoReleaser output

Author: davegaeddert

install.sh

@@ -7,15 +7,15 @@ INSTALL_DIR="${INSTALL_DIR:-/usr/local/bin}"
 # Detect OS
 OS=$(uname -s | tr '[:upper:]' '[:lower:]')
 case "$OS" in
-    linux)  OS="Linux" ;;
-    darwin) OS="Darwin" ;;
+    linux)  ;;
+    darwin) ;;
     *)      echo "Unsupported OS: $OS"; exit 1 ;;
 esac
 
 # Detect architecture
 ARCH=$(uname -m)
 case "$ARCH" in
-    x86_64|amd64)  ARCH="x86_64" ;;
+    x86_64|amd64)  ARCH="amd64" ;;
     arm64|aarch64) ARCH="arm64" ;;
     *)             echo "Unsupported architecture: $ARCH"; exit 1 ;;
 esac