Add COMPOUND node execution and S-expression API

- Execute COMPOUND nodes with combined FFmpeg filter chain
- Handle TRANSFORM, RESIZE, SEGMENT filters in chain
- Migrate orchestrator to S-expression recipes (remove YAML)
- Update API endpoints to use recipe_sexp parameter
- Extract analysis nodes from recipe for dynamic analysis

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

app/routers/api.py

@@ -11,7 +11,6 @@ import uuid
 from datetime import datetime, timezone
 from typing import Dict, List, Optional
 
-import yaml
 from fastapi import APIRouter, Depends, HTTPException
 from pydantic import BaseModel
 
@@ -26,9 +25,8 @@ RUNS_KEY_PREFIX = "artdag:run:"
 
 
 class PlanRequest(BaseModel):
-    recipe_yaml: str
+    recipe_sexp: str
     input_hashes: Dict[str, str]
-    features: List[str] = ["beats", "energy"]
 
 
 class ExecutePlanRequest(BaseModel):
@@ -37,9 +35,8 @@ class ExecutePlanRequest(BaseModel):
 
 
 class RecipeRunRequest(BaseModel):
-    recipe_yaml: str
+    recipe_sexp: str
     input_hashes: Dict[str, str]
-    features: List[str] = ["beats", "energy"]
 
 
 def compute_run_id(input_hashes: List[str], recipe: str, recipe_hash: str = None) -> str:
@@ -68,9 +65,8 @@ async def generate_plan_endpoint(
 
     try:
         task = generate_plan.delay(
-            recipe_yaml=request.recipe_yaml,
+            recipe_sexp=request.recipe_sexp,
             input_hashes=request.input_hashes,
-            features=request.features,
         )
 
         # Wait for result (plan generation is usually fast)
@@ -136,15 +132,16 @@ async def run_recipe_endpoint(
     Returns immediately with run_id. Poll /api/run/{run_id} for status.
     """
     from tasks.orchestrate import run_recipe
+    from artdag.sexp import compile_string
     import database
 
     redis = get_redis_client()
     cache = get_cache_manager()
 
-    # Parse recipe name
+    # Parse recipe name from S-expression
     try:
-        recipe_data = yaml.safe_load(request.recipe_yaml)
-        recipe_name = recipe_data.get("name", "unknown")
+        compiled = compile_string(request.recipe_sexp)
+        recipe_name = compiled.name or "unknown"
     except Exception:
         recipe_name = "unknown"
 
@@ -152,7 +149,7 @@ async def run_recipe_endpoint(
     run_id = compute_run_id(
         list(request.input_hashes.values()),
         recipe_name,
-        hashlib.sha3_256(request.recipe_yaml.encode()).hexdigest()
+        hashlib.sha3_256(request.recipe_sexp.encode()).hexdigest()
     )
 
     # Check if already completed
@@ -171,9 +168,8 @@ async def run_recipe_endpoint(
     # Submit to Celery
     try:
         task = run_recipe.delay(
-            recipe_yaml=request.recipe_yaml,
+            recipe_sexp=request.recipe_sexp,
             input_hashes=request.input_hashes,
-            features=request.features,
             run_id=run_id,
         )