feat: Add Comfy Agent service for NODE3 image/video generation

- Create comfy-agent service with FastAPI + NATS integration
- ComfyUI client with HTTP/WebSocket support
- REST API: /generate/image, /generate/video, /status, /result
- NATS subjects: agent.invoke.comfy, comfy.request.*
- Async job queue with progress tracking
- Docker compose configuration for NODE3
- Update PROJECT-MASTER-INDEX.md with NODE2/NODE3 docs

Co-Authored-By: Warp <agent@warp.dev>

services/comfy-agent/app/comfyui_client.py

@@ -0,0 +1,54 @@
+# services/comfy-agent/app/comfyui_client.py
+import asyncio
+import httpx
+import json
+import websockets
+from typing import Any, Dict, Optional, Callable
+from .config import settings
+
+ProgressCb = Callable[[float, str], None]
+
+class ComfyUIClient:
+    def __init__(self) -> None:
+        self.http = httpx.AsyncClient(base_url=settings.COMFYUI_HTTP, timeout=60)
+
+    async def queue_prompt(self, prompt_graph: Dict[str, Any], client_id: str) -> str:
+        # ComfyUI expects: {"prompt": {...}, "client_id": "..."}
+        r = await self.http.post("/prompt", json={"prompt": prompt_graph, "client_id": client_id})
+        r.raise_for_status()
+        data = r.json()
+        # typically returns {"prompt_id": "...", "number": ...}
+        return data["prompt_id"]
+
+    async def wait_progress(self, client_id: str, prompt_id: str, on_progress: Optional[ProgressCb] = None) -> None:
+        # WS emits progress/executing/status; keep generic handling
+        ws_url = f"{settings.COMFYUI_WS}?clientId={client_id}"
+        async with websockets.connect(ws_url, max_size=50_000_000) as ws:
+            while True:
+                msg = await ws.recv()
+                evt = json.loads(msg)
+
+                # Best-effort progress mapping
+                if evt.get("type") == "progress":
+                    data = evt.get("data", {})
+                    max_v = float(data.get("max", 1.0))
+                    val = float(data.get("value", 0.0))
+                    p = 0.0 if max_v <= 0 else min(1.0, val / max_v)
+                    if on_progress:
+                        on_progress(p, "progress")
+
+                # completion signal varies; "executing" with node=None часто означає done
+                if evt.get("type") == "executing":
+                    data = evt.get("data", {})
+                    if data.get("prompt_id") == prompt_id and data.get("node") is None:
+                        if on_progress:
+                            on_progress(1.0, "done")
+                        return
+
+    async def get_history(self, prompt_id: str) -> Dict[str, Any]:
+        r = await self.http.get(f"/history/{prompt_id}")
+        r.raise_for_status()
+        return r.json()
+
+    async def close(self) -> None:
+        await self.http.aclose()