Fix get_recipe to handle both YAML and S-expression formats

The upload endpoint accepts both YAML and S-expression recipes, but
get_recipe only tried to parse S-expression. Now it detects the format
and parses accordingly.

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

app/services/recipe_service.py

@@ -32,6 +32,8 @@ class RecipeService:
 
     async def get_recipe(self, recipe_id: str) -> Optional[Recipe]:
         """Get a recipe by ID (content hash)."""
+        import yaml
+
         # Get from cache (content-addressed storage)
         path = self.cache.get_by_cid(recipe_id)
         if not path or not path.exists():
@@ -40,13 +42,34 @@ class RecipeService:
         with open(path) as f:
             content = f.read()
 
-        # Parse S-expression
-        try:
-            compiled = compile_string(content)
-            recipe_data = compiled.to_dict()
-            recipe_data["sexp"] = content
-        except (ParseError, CompileError) as e:
-            return {"error": str(e), "recipe_id": recipe_id}
+        # Detect format - check if it starts with ( after skipping comments
+        def is_sexp_format(text):
+            for line in text.split('\n'):
+                stripped = line.strip()
+                if not stripped or stripped.startswith(';'):
+                    continue
+                return stripped.startswith('(')
+            return False
+
+        if is_sexp_format(content):
+            # Parse S-expression
+            try:
+                compiled = compile_string(content)
+                recipe_data = compiled.to_dict()
+                recipe_data["sexp"] = content
+                recipe_data["format"] = "sexp"
+            except (ParseError, CompileError) as e:
+                return {"error": str(e), "recipe_id": recipe_id}
+        else:
+            # Parse YAML
+            try:
+                recipe_data = yaml.safe_load(content)
+                if not isinstance(recipe_data, dict):
+                    return {"error": "Invalid YAML: expected dictionary", "recipe_id": recipe_id}
+                recipe_data["yaml"] = content
+                recipe_data["format"] = "yaml"
+            except yaml.YAMLError as e:
+                return {"error": f"YAML parse error: {e}", "recipe_id": recipe_id}
 
         # Add the recipe_id to the data for convenience
         recipe_data["recipe_id"] = recipe_id
@@ -56,8 +79,12 @@ class RecipeService:
         if ipfs_cid:
             recipe_data["ipfs_cid"] = ipfs_cid
 
-        # Compute step_count from nodes
-        nodes = recipe_data.get("dag", {}).get("nodes", [])
+        # Compute step_count from nodes (handle both formats)
+        if recipe_data.get("format") == "sexp":
+            nodes = recipe_data.get("dag", {}).get("nodes", [])
+        else:
+            # YAML format: nodes might be at top level or under dag
+            nodes = recipe_data.get("nodes", recipe_data.get("dag", {}).get("nodes", []))
         recipe_data["step_count"] = len(nodes) if isinstance(nodes, (list, dict)) else 0
 
         return recipe_data