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/api.py

@@ -0,0 +1,51 @@
+# services/comfy-agent/app/api.py
+from fastapi import APIRouter, HTTPException
+from .models import GenerateImageRequest, GenerateVideoRequest, JobStatus
+from .jobs import JOB_STORE
+from .worker import enqueue
+
+router = APIRouter()
+
+def _build_workflow_t2i(req: GenerateImageRequest) -> dict:
+    # MVP: placeholder graph; you will replace with your canonical Comfy workflow JSON.
+    # Keep it deterministic and param-driven.
+    return {
+        "1": {"class_type": "CLIPTextEncode", "inputs": {"text": req.prompt, "clip": ["2", 0]}},
+        "2": {"class_type": "CheckpointLoaderSimple", "inputs": {"ckpt_name": "sdxl.safetensors"}},
+        # TODO: Add complete workflow JSON for text-to-image
+    }
+
+def _build_workflow_t2v(req: GenerateVideoRequest) -> dict:
+    # MVP placeholder for LTX-2 pipeline; replace with actual LTX-2 workflow.
+    return {
+        "1": {"class_type": "CLIPTextEncode", "inputs": {"text": req.prompt, "clip": ["2", 0]}},
+        # TODO: Add complete workflow JSON for text-to-video with LTX-2
+    }
+
+@router.post("/generate/image", response_model=JobStatus)
+async def generate_image(req: GenerateImageRequest):
+    job = JOB_STORE.create("text-to-image")
+    graph = _build_workflow_t2i(req)
+    enqueue(job.job_id, "text-to-image", graph)
+    return JOB_STORE.get(job.job_id)
+
+@router.post("/generate/video", response_model=JobStatus)
+async def generate_video(req: GenerateVideoRequest):
+    job = JOB_STORE.create("text-to-video")
+    graph = _build_workflow_t2v(req)
+    enqueue(job.job_id, "text-to-video", graph)
+    return JOB_STORE.get(job.job_id)
+
+@router.get("/status/{job_id}", response_model=JobStatus)
+async def status(job_id: str):
+    job = JOB_STORE.get(job_id)
+    if not job:
+        raise HTTPException(status_code=404, detail="job_not_found")
+    return job
+
+@router.get("/result/{job_id}", response_model=JobStatus)
+async def result(job_id: str):
+    job = JOB_STORE.get(job_id)
+    if not job:
+        raise HTTPException(status_code=404, detail="job_not_found")
+    return job