fix: search analytics crashes recording when the JSON file predates a counter (#1224)

* refactor: single _default_analytics() instead of duplicated default dicts

* fix: merge analytics defaults so an old/partial file doesn't KeyError on record

* test: analytics load merges defaults; record survives a partial file

src/search/analytics.py

@@ -45,32 +45,37 @@ class RateLimitError(SearchEngineError):
 # ----------------------------------------------------------------------
 # Analytics helpers
 # ----------------------------------------------------------------------
+def _default_analytics() -> Dict[str, Any]:
+    """A fresh analytics document with every counter present."""
+    return {
+        "total_queries": 0,
+        "successful_queries": 0,
+        "failed_queries": 0,
+        "cache_hits": 0,
+        "cache_misses": 0,
+        "query_patterns": {},
+    }
+
+
 def _load_analytics() -> Dict[str, Any]:
     """Load analytics data from the JSON file, creating defaults if missing."""
     if not ANALYTICS_FILE.exists():
-        default = {
-            "total_queries": 0,
-            "successful_queries": 0,
-            "failed_queries": 0,
-            "cache_hits": 0,
-            "cache_misses": 0,
-            "query_patterns": {},
-        }
+        default = _default_analytics()
         _save_analytics(default)
         return default
     try:
         with open(ANALYTICS_FILE, "r", encoding="utf-8") as f:
-            return json.load(f)
+            data = json.load(f)
+        # Merge over defaults so a file written by an older schema (or a
+        # partial write) still has every counter — _record_query indexes
+        # these keys directly and would otherwise raise KeyError.
+        merged = _default_analytics()
+        if isinstance(data, dict):
+            merged.update(data)
+        return merged
     except Exception as e:
         logger.warning(f"Failed to load analytics file: {e}")
-        return {
-            "total_queries": 0,
-            "successful_queries": 0,
-            "failed_queries": 0,
-            "cache_hits": 0,
-            "cache_misses": 0,
-            "query_patterns": {},
-        }
+        return _default_analytics()
 
 
 def _save_analytics(data: Dict[str, Any]) -> None: