sterilize hot-fixes: 300s timeout + defensive string→dict parsing

Two failures surfaced by job 6 with the bigger prompt (full Mealie food
catalog ~50KB + recipe context with steps + spell-cleanup rules):

1. quinoa-chili-with-sweet-potatoes: 180s timeout. The bigger prompt
   means Sonnet has more to chew through per call. Bumped _parse_batch
   timeout 180s → 300s. Recipes with many ingredients now get more
   slack before clawdforge gives up.

2. salmon-sushi-bake: "unexpected response shape" — Sonnet returned
   the JSON as a STRING rather than a parsed dict (depends on size +
   how clawdforge unwraps the response). _parse_batch was strictly
   requiring isinstance(result, dict) and rejecting strings outright,
   leaving the recipe in error state with valid JSON visible in the
   error message. Added defensive string→dict parsing (with optional
   code-fence stripping) mirroring the pattern already used by
   forge._extract_food_info.

Both errored recipes from job 6 can now be re-run cleanly. Apply path
unchanged — defensive food.id preservation from 6bcf79e still in
effect.

cauldron/sterilizer.py

@@ -533,12 +533,28 @@ class Sterilizer:
                 prompt=prompt,
                 model=self.model,
                 system=self._system_prompt(),
-                timeout_secs=180,
+                timeout_secs=300,
             )
         except ForgeError as e:
             raise RuntimeError(f"clawdforge failed: {e}") from e
 
         result = resp.get("result")
+        # Sonnet sometimes returns the JSON as a string rather than a parsed
+        # dict (depends on output size + clawdforge's parsing). Defensively
+        # parse if so, mirroring forge._extract_food_info's pattern.
+        if isinstance(result, str):
+            try:
+                stripped = result.strip()
+                # Strip optional code fences
+                if stripped.startswith("```"):
+                    import re as _re
+                    stripped = _re.sub(r"^```(?:json)?\s*", "", stripped)
+                    stripped = _re.sub(r"\s*```$", "", stripped)
+                result = json.loads(stripped)
+            except Exception:
+                # Fall through to the shape-check below; will raise with
+                # the (truncated) original string for debugging
+                pass
         if not isinstance(result, dict) or "parses" not in result:
             raise RuntimeError(f"unexpected response shape: {str(result)[:200]}")