feat: initial ComfyUI workflow templates extension

- 40 workflow templates (text-to-image, image-to-video, image-to-image,
  text-to-music, upscaling, advanced, nsfw)
- Color-coded placeholder preview images using Pillow
- Template-only extension (no custom nodes)
- Preview generation script for future workflow additions

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

scripts/generate_previews.py

@@ -0,0 +1,120 @@
+#!/usr/bin/env python3
+"""Generate placeholder preview images for ComfyUI workflow templates."""
+
+from pathlib import Path
+from PIL import Image, ImageDraw, ImageFont
+
+PREVIEW_WIDTH = 512
+PREVIEW_HEIGHT = 288  # 16:9 aspect ratio
+
+# Category colors based on filename patterns
+# Order matters: more specific patterns first, generic ones last
+CATEGORY_COLORS = {
+    # NSFW patterns (check first - most specific)
+    "lustify": "#9B2C2C",      # Dark red - NSFW
+    "realvis": "#9B2C2C",      # Dark red - NSFW
+    "pony": "#9B2C2C",         # Dark red - NSFW
+    "nsfw": "#9B2C2C",         # Dark red - NSFW
+    # Advanced patterns
+    "animatediff": "#4ad9d9",  # Cyan - advanced
+    "controlnet": "#4ad9d9",   # Cyan - advanced
+    "batch": "#4ad9d9",        # Cyan - advanced
+    # Upscaling
+    "upscale": "#9b4ad9",      # Purple - upscaling
+    # Generic type patterns (check last)
+    "t2i": "#4a90d9",          # Blue - text-to-image
+    "i2v": "#d94a4a",          # Red - image-to-video
+    "i2i": "#4ad96b",          # Green - image-to-image
+    "t2m": "#d9a04a",          # Orange - text-to-music
+    "m2m": "#d9a04a",          # Orange - music-to-music
+}
+DEFAULT_COLOR = "#2d2d2d"
+
+
+def get_color_for_workflow(filename: str) -> str:
+    """Determine background color based on filename."""
+    lower = filename.lower()
+    for pattern, color in CATEGORY_COLORS.items():
+        if pattern in lower:
+            return color
+    return DEFAULT_COLOR
+
+
+def humanize_filename(filename: str) -> str:
+    """Convert filename to readable title."""
+    # Remove extension and common suffixes
+    name = filename.replace('.json', '')
+    name = name.replace('-production-v1', '')
+    name = name.replace('-production', '')
+    name = name.replace('-v1', '')
+    # Replace separators with spaces
+    name = name.replace('-', ' ').replace('_', ' ')
+    # Title case
+    return name.title()
+
+
+def generate_preview(json_path: Path, output_path: Path):
+    """Generate a placeholder preview image with workflow title."""
+    filename = json_path.name
+    bg_color = get_color_for_workflow(filename)
+    title = humanize_filename(filename)
+
+    # Create image
+    img = Image.new('RGB', (PREVIEW_WIDTH, PREVIEW_HEIGHT), bg_color)
+    draw = ImageDraw.Draw(img)
+
+    # Try to load fonts
+    try:
+        title_font = ImageFont.truetype(
+            "/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf", 24
+        )
+    except OSError:
+        title_font = ImageFont.load_default()
+
+    # Word wrap title
+    words = title.split()
+    lines = []
+    current_line = ""
+    for word in words:
+        test = f"{current_line} {word}".strip()
+        if len(test) > 28:
+            if current_line:
+                lines.append(current_line)
+            current_line = word
+        else:
+            current_line = test
+    if current_line:
+        lines.append(current_line)
+
+    # Draw centered text
+    y_offset = PREVIEW_HEIGHT // 2 - (len(lines) * 30) // 2
+    for line in lines:
+        bbox = draw.textbbox((0, 0), line, font=title_font)
+        text_width = bbox[2] - bbox[0]
+        x = (PREVIEW_WIDTH - text_width) // 2
+        draw.text((x, y_offset), line, fill="white", font=title_font)
+        y_offset += 30
+
+    img.save(output_path, 'JPEG', quality=85)
+
+
+def main():
+    workflows_dir = Path(__file__).parent.parent / 'example_workflows'
+
+    count = 0
+    for json_file in sorted(workflows_dir.glob('*.json')):
+        preview_path = json_file.with_suffix('.jpg')
+
+        if preview_path.exists():
+            print(f"Skipping (exists): {json_file.name}")
+            continue
+
+        generate_preview(json_file, preview_path)
+        print(f"Generated: {preview_path.name}")
+        count += 1
+
+    print(f"\nDone! Generated {count} preview images.")
+
+
+if __name__ == '__main__':
+    main()