Refactor CLI and add preprocessing pipeline

- New CLI structure: -p project, -a action (required flags)
- Add -i import, -f force, -v verbose, --dry-run, --no-cache options
- Add preprocessor.py with chroma key filter (ProRes 4444 output)
- Support background images from shared_assets folder
- Support video metadata JSON files (talkinghead.json)
- Add validation for preprocessed output before render
- Update gnommo.sh with import command and new CLI interface
- Fix Python 3.9 compatibility (Optional[] instead of | None)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

gnommo.sh

@@ -4,7 +4,9 @@
 #
 # Usage:
 #   gnommo.sh -p <project>              Render project
+#   gnommo.sh -p <project> import       Generate slides.json from image files
 #   gnommo.sh -p <project> validate     Validate only
+#   gnommo.sh -p <project> preprocess   Apply video preprocessing filters
 #   gnommo.sh -p <project> transcribe   Transcribe video
 #   gnommo.sh -p <project> align        Align markers to transcript
 #   gnommo.sh -p <project> all          Full pipeline: transcribe → align → render
@@ -26,13 +28,16 @@ fi
 PROJECT=""
 COMMAND="render"
 VERBOSE=""
+FORCE=""
 
 usage() {
     echo "Usage: gnommo.sh -p <project> [command] [options]"
     echo ""
     echo "Commands:"
     echo "  render      Render video (default)"
+    echo "  import      Generate slides.json from image files"
     echo "  validate    Validate project only"
+    echo "  preprocess  Apply video preprocessing filters (chroma key, etc.)"
     echo "  transcribe  Transcribe video audio"
     echo "  align       Align manuscript to transcript"
     echo "  all         Full pipeline: transcribe → align → render"
@@ -40,10 +45,13 @@ usage() {
     echo "Options:"
     echo "  -p <dir>    Project directory (required)"
     echo "  -v          Verbose output"
+    echo "  -f          Force overwrite existing files"
     echo "  -h          Show this help"
     echo ""
     echo "Examples:"
     echo "  gnommo.sh -p video1              # Render video1 project"
+    echo "  gnommo.sh -p video1 import       # Generate slides.json"
+    echo "  gnommo.sh -p video1 import -f    # Force overwrite slides.json"
     echo "  gnommo.sh -p video1 validate     # Validate only"
     echo "  gnommo.sh -p video1 all          # Full pipeline"
     exit 0
@@ -56,13 +64,17 @@ while [[ $# -gt 0 ]]; do
             shift 2
             ;;
         -v|--verbose)
-            VERBOSE="--verbose"
+            VERBOSE="-v"
+            shift
+            ;;
+        -f|--force)
+            FORCE="-f"
             shift
             ;;
         -h|--help)
             usage
             ;;
-        validate|render|transcribe|align|all)
+        import|validate|render|preprocess|transcribe|align|all)
             COMMAND="$1"
             shift
             ;;
@@ -90,64 +102,49 @@ if [[ ! -f "$PROJECT/project.json" ]]; then
     exit 1
 fi
 
-# Run commands
+# Run commands using new CLI interface
 run_gnommo() {
-    "$VENV_PYTHON" -m gnommo "$@"
+    "$VENV_PYTHON" -m gnommo -p "$PROJECT" -a "$1" $VERBOSE
+}
+
+run_gnommo_import() {
+    "$VENV_PYTHON" -m gnommo -p "$PROJECT" -a validate -i $FORCE $VERBOSE
 }
 
 case $COMMAND in
+    import)
+        echo "=== Importing assets for $PROJECT ==="
+        run_gnommo_import
+        ;;
+
     validate)
         echo "=== Validating $PROJECT ==="
-        run_gnommo validate "$PROJECT"
+        run_gnommo validate
         ;;
 
     transcribe)
         echo "=== Transcribing $PROJECT ==="
-        VIDEO=$(find "$PROJECT/media" -name "*.mov" -o -name "*.mp4" | head -1)
-        if [[ -z "$VIDEO" ]]; then
-            echo "Error: No video file found in $PROJECT/media/"
-            exit 1
-        fi
-        run_gnommo transcribe "$VIDEO"
+        run_gnommo transcribe
         ;;
 
     align)
         echo "=== Aligning $PROJECT ==="
-        run_gnommo align "$PROJECT"
+        run_gnommo align
         ;;
 
     render)
         echo "=== Rendering $PROJECT ==="
-        run_gnommo render "$PROJECT" $VERBOSE
+        run_gnommo render
+        ;;
+
+    preprocess)
+        echo "=== Preprocessing $PROJECT ==="
+        run_gnommo preprocess
         ;;
 
     all)
         echo "=== Full Pipeline: $PROJECT ==="
-        echo ""
-
-        # Step 1: Transcribe
-        echo ">>> Step 1/3: Transcribe"
-        VIDEO=$(find "$PROJECT/media" -name "*.mov" -o -name "*.mp4" | grep -v transcript | head -1)
-        if [[ -z "$VIDEO" ]]; then
-            echo "Error: No video file found in $PROJECT/media/"
-            exit 1
-        fi
-        TRANSCRIPT="${VIDEO%.*}.transcript.json"
-        if [[ -f "$TRANSCRIPT" ]]; then
-            echo "    Transcript exists, skipping: $TRANSCRIPT"
-        else
-            run_gnommo transcribe "$VIDEO"
-        fi
-        echo ""
-
-        # Step 2: Align
-        echo ">>> Step 2/3: Align"
-        run_gnommo align "$PROJECT"
-        echo ""
-
-        # Step 3: Render
-        echo ">>> Step 3/3: Render"
-        run_gnommo render "$PROJECT" $VERBOSE
+        run_gnommo all
         ;;
 
     *)