fix: route log output to stdout for SSH visibility

All log_* functions were writing to stderr, causing output to be
invisible in SSH sessions where stderr is not forwarded or captured.

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

scripts/arty.sh

@@ -43,29 +43,29 @@ declare -g -A ARTY_INSTALL_STACK
 
 # Logging functions
 log_info() {
-  echo -e "${BLUE}[INFO]${NC} $1" >&2
+  echo -e "${BLUE}[INFO]${NC} $1"
 }
 
 log_success() {
-  echo -e "${GREEN}[ok]${NC} $1" >&2
+  echo -e "${GREEN}[ok]${NC} $1"
 }
 
 log_warn() {
-  echo -e "${YELLOW}[!]${NC} $1" >&2
+  echo -e "${YELLOW}[!]${NC} $1"
 }
 
 log_error() {
-  echo -e "${RED}[x]${NC} $1" >&2
+  echo -e "${RED}[x]${NC} $1"
 }
 
 log_debug() {
   if [[ "$ARTY_VERBOSE" == "1" ]]; then
-    echo -e "${CYAN}[DEBUG]${NC} $1" >&2
+    echo -e "${CYAN}[DEBUG]${NC} $1"
   fi
 }
 
 log_step() {
-  echo -e "${CYAN}[!]${NC} $1" >&2
+  echo -e "${CYAN}[!]${NC} $1"
 }
 
 # ============================================================================