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>

example_workflows/musicgen-melody-t2m-production-v1.json

@@ -0,0 +1,150 @@
+{
+  "last_node_id": 2,
+  "last_link_id": 1,
+  "nodes": [
+    {
+      "id": 1,
+      "type": "Musicgen_",
+      "pos": [50, 100],
+      "size": [400, 300],
+      "flags": {},
+      "order": 0,
+      "mode": 0,
+      "outputs": [
+        {
+          "name": "audio",
+          "type": "AUDIO",
+          "links": [1],
+          "slot_index": 0
+        }
+      ],
+      "properties": {
+        "Node name for S&R": "Musicgen_"
+      },
+      "widgets_values": [
+        "Electronic music with melodic elements and catchy hooks",
+        30.0,
+        3.5,
+        42,
+        "auto"
+      ],
+      "title": "MusicGen Melody Generator"
+    },
+    {
+      "id": 2,
+      "type": "AudioPlay",
+      "pos": [500, 100],
+      "size": [315, 100],
+      "flags": {},
+      "order": 1,
+      "mode": 0,
+      "inputs": [
+        {
+          "name": "audio",
+          "type": "AUDIO",
+          "link": 1
+        }
+      ],
+      "properties": {
+        "Node name for S&R": "AudioPlay"
+      },
+      "title": "API Audio Output"
+    }
+  ],
+  "links": [
+    [1, 1, 0, 2, 0, "AUDIO"]
+  ],
+  "groups": [],
+  "config": {},
+  "extra": {
+    "workflow_info": {
+      "name": "MusicGen Melody Text-to-Music Production",
+      "version": "1.2.0",
+      "description": "Music generation using MusicGen with melodic focus. Note: Melody conditioning via audio input not yet supported.",
+      "category": "text-to-music",
+      "tags": ["musicgen", "melody", "t2m", "audio", "production"],
+      "requirements": {
+        "models": ["facebook/musicgen-melody"],
+        "custom_nodes": ["comfyui-sound-lab"],
+        "vram_min": "10GB",
+        "vram_recommended": "12GB"
+      },
+      "parameters": {
+        "prompt": {
+          "node_id": 1,
+          "widget_index": 0,
+          "type": "string",
+          "required": true,
+          "default": "Electronic music with melodic elements",
+          "description": "Text description of desired music style, genre, mood, instruments"
+        },
+        "duration": {
+          "node_id": 1,
+          "widget_index": 1,
+          "type": "float",
+          "required": false,
+          "default": 30.0,
+          "min": 1.0,
+          "max": 60.0,
+          "description": "Duration in seconds (up to 30s recommended for best quality)"
+        },
+        "guidance_scale": {
+          "node_id": 1,
+          "widget_index": 2,
+          "type": "float",
+          "required": false,
+          "default": 3.5,
+          "min": 0.0,
+          "max": 20.0,
+          "description": "How closely to follow the prompt (3.5 recommended)"
+        },
+        "seed": {
+          "node_id": 1,
+          "widget_index": 3,
+          "type": "integer",
+          "required": false,
+          "default": 42,
+          "min": 0,
+          "max": 2147483647,
+          "description": "Random seed for reproducibility"
+        },
+        "device": {
+          "node_id": 1,
+          "widget_index": 4,
+          "type": "string",
+          "required": false,
+          "default": "auto",
+          "options": ["auto", "cpu"],
+          "description": "Computation device (auto recommended)"
+        }
+      },
+      "outputs": {
+        "audio": {
+          "node_id": 2,
+          "type": "audio",
+          "format": "FLAC",
+          "sample_rate": "32000 Hz",
+          "channels": "stereo"
+        }
+      },
+      "performance": {
+        "avg_generation_time": "40-60 seconds for 30s audio",
+        "vram_usage": "~10-12GB",
+        "gpu_utilization": "90-100%"
+      },
+      "use_cases": [
+        "Melodic music generation",
+        "Creating catchy hooks and melodies",
+        "Music with strong melodic structure"
+      ],
+      "notes": [
+        "IMPORTANT: Melody conditioning via audio input not yet supported in current Sound Lab implementation",
+        "This workflow uses text prompts only - describe melodic characteristics in the prompt",
+        "For best melodic results, use descriptive terms like 'catchy melody', 'melodic hooks', 'harmonic progression'",
+        "MusicGen Melody model trained for melodic content",
+        "Output is 32kHz stereo FLAC format"
+      ]
+    }
+  },
+  "version": 0.4
+}