Remove YAML support - S-expressions only

- Recipe service now only handles S-expressions
- Removed yaml import and all YAML parsing code
- Plans are just node outputs - cached by content hash
- Run service looks up plans from cache, falls back to legacy dir

Code is data. Everything is S-expressions.

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

app/services/run_service.py

@@ -481,14 +481,36 @@ class RunService:
         return True, None
 
     async def get_run_plan(self, run_id: str) -> Optional[Dict[str, Any]]:
-        """Get execution plan for a run."""
-        # Prefer S-expression plan
+        """Get execution plan for a run.
+
+        Plans are just node outputs - cached by content hash like everything else.
+        """
+        # Get run to find plan_cache_id
+        run = await self.get_run(run_id)
+        if not run:
+            return None
+
+        plan_cache_id = run.get("plan_cache_id")
+        if plan_cache_id:
+            # Get plan from cache by content hash
+            plan_path = self.cache.get_by_content_hash(plan_cache_id)
+            if plan_path and plan_path.exists():
+                with open(plan_path) as f:
+                    content = f.read()
+                    # Detect format
+                    if content.strip().startswith("("):
+                        return {"sexp": content, "format": "sexp"}
+                    else:
+                        plan = json.loads(content)
+                        plan["format"] = "json"
+                        return plan
+
+        # Fall back to legacy plans directory
         sexp_path = self.cache_dir / "plans" / f"{run_id}.sexp"
         if sexp_path.exists():
             with open(sexp_path) as f:
                 return {"sexp": f.read(), "format": "sexp"}
 
-        # Fall back to JSON for legacy plans
         json_path = self.cache_dir / "plans" / f"{run_id}.json"
         if json_path.exists():
             with open(json_path) as f:
@@ -500,10 +522,9 @@ class RunService:
 
     async def get_run_plan_sexp(self, run_id: str) -> Optional[str]:
         """Get execution plan as S-expression string."""
-        sexp_path = self.cache_dir / "plans" / f"{run_id}.sexp"
-        if sexp_path.exists():
-            with open(sexp_path) as f:
-                return f.read()
+        plan = await self.get_run_plan(run_id)
+        if plan and plan.get("format") == "sexp":
+            return plan.get("sexp")
         return None
 
     async def get_run_artifacts(self, run_id: str) -> List[Dict[str, Any]]: