fix: robust ISO download detection, fix color escape codes in installer

- Use find instead of hardcoded filename for downloaded ISO detection
  (wget may save with redirect filename or partial name)
- Fix color escape codes: use $'\033' syntax instead of '\033' for
  reliable ANSI color rendering in installer output

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

image-recipe/build-auto-installer-iso.sh

@@ -431,13 +431,14 @@ if [ ! -f "$BASE_ISO" ]; then
             exit 1
         }
         
-        # Find the downloaded file (wget creates it with a name like "download" or the actual filename)
-        if [ -f "download" ]; then
-            mv "download" "$BASE_ISO"
-        elif [ -f "debian-live-12.10.0-${DEB_ARCH}-standard.iso" ]; then
-            mv "debian-live-12.10.0-${DEB_ARCH}-standard.iso" "$BASE_ISO"
+        # Find the downloaded file — wget may use URL filename or follow redirects
+        FOUND_ISO=$(find "$WORK_DIR" -maxdepth 1 -name "debian-live-12*.iso" -o -name "download" 2>/dev/null | head -1)
+        if [ -n "$FOUND_ISO" ] && [ -f "$FOUND_ISO" ]; then
+            mv "$FOUND_ISO" "$BASE_ISO"
         else
-            echo "   ❌ Downloaded file not found"
+            echo "   ❌ Downloaded file not found in $WORK_DIR"
+            echo "   Files present:"
+            ls -la "$WORK_DIR"/*.iso 2>/dev/null || echo "   (no .iso files)"
             exit 1
         fi
     else
@@ -974,12 +975,12 @@ case "$(uname -m)" in
         ;;
 esac
 
-# Colors
-RED='\033[0;31m'
-GREEN='\033[0;32m'
-YELLOW='\033[1;33m'
-BLUE='\033[0;34m'
-NC='\033[0m'
+# Colors (use $'...' syntax for reliable escape code interpretation)
+RED=$'\033[0;31m'
+GREEN=$'\033[0;32m'
+YELLOW=$'\033[1;33m'
+BLUE=$'\033[0;34m'
+NC=$'\033[0m'
 
 clear
 echo ""