Add streaming endpoint to runs router

- Add /runs/stream POST endpoint for streaming recipes
- Accepts recipe_sexp, sources_sexp, audio_sexp
- Submits to run_stream Celery task

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

app/routers/runs.py

@@ -113,6 +113,16 @@ class RunStatus(BaseModel):
     infrastructure: Optional[Dict[str, Any]] = None
 
 
+class StreamRequest(BaseModel):
+    """Request to run a streaming recipe."""
+    recipe_sexp: str  # The recipe S-expression content
+    output_name: str = "output.mp4"
+    duration: Optional[float] = None  # Duration in seconds
+    fps: Optional[float] = None  # FPS override
+    sources_sexp: Optional[str] = None  # Sources config S-expression
+    audio_sexp: Optional[str] = None  # Audio config S-expression
+
+
 def get_run_service():
     """Get run service instance."""
     import database
@@ -142,6 +152,64 @@ async def create_run(
     return run
 
 
+@router.post("/stream", response_model=RunStatus)
+async def create_stream_run(
+    request: StreamRequest,
+    ctx: UserContext = Depends(require_auth),
+    redis = Depends(get_redis_client),
+):
+    """Start a streaming video render.
+
+    The recipe_sexp should be a complete streaming recipe with
+    (stream ...) form defining the pipeline.
+
+    Assets can be referenced by CID or friendly name in the recipe.
+    """
+    import uuid
+    from tasks.streaming import run_stream
+
+    run_id = str(uuid.uuid4())
+    created_at = datetime.now(timezone.utc).isoformat()
+
+    # Submit Celery task
+    task = run_stream.delay(
+        recipe_sexp=request.recipe_sexp,
+        output_name=request.output_name,
+        duration=request.duration,
+        fps=request.fps,
+        actor_id=ctx.actor_id,
+        sources_sexp=request.sources_sexp,
+        audio_sexp=request.audio_sexp,
+    )
+
+    # Store run metadata in Redis
+    run_data = {
+        "run_id": run_id,
+        "status": "pending",
+        "recipe": "streaming",
+        "actor_id": ctx.actor_id,
+        "created_at": created_at,
+        "celery_task_id": task.id,
+        "output_name": request.output_name,
+    }
+
+    await redis.set(
+        f"{RUNS_KEY_PREFIX}{run_id}",
+        json.dumps(run_data),
+        ex=86400 * 7  # 7 days
+    )
+
+    logger.info(f"Started stream run {run_id} with task {task.id}")
+
+    return RunStatus(
+        run_id=run_id,
+        status="pending",
+        recipe="streaming",
+        created_at=created_at,
+        celery_task_id=task.id,
+    )
+
+
 @router.get("/{run_id}")
 async def get_run(
     request: Request,