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

tests/test_search_analytics_defaults.py

@@ -0,0 +1,33 @@
+"""Tests for analytics default-merge on load (src/search/analytics.py)."""
+import json
+
+import src.search.analytics as analytics
+
+
+def test_load_merges_defaults_for_partial_file(tmp_path, monkeypatch):
+    # A file written by an older schema is missing most counters.
+    f = tmp_path / "search_analytics.json"
+    f.write_text(json.dumps({"total_queries": 5}), encoding="utf-8")
+    monkeypatch.setattr(analytics, "ANALYTICS_FILE", f)
+
+    data = analytics._load_analytics()
+
+    # Existing value preserved, every missing counter filled with its default.
+    assert data["total_queries"] == 5
+    assert data["query_patterns"] == {}
+    for key in ("successful_queries", "failed_queries", "cache_hits", "cache_misses"):
+        assert data[key] == 0
+
+
+def test_record_query_survives_partial_file(tmp_path, monkeypatch):
+    f = tmp_path / "search_analytics.json"
+    f.write_text(json.dumps({"total_queries": 1}), encoding="utf-8")
+    monkeypatch.setattr(analytics, "ANALYTICS_FILE", f)
+
+    # Before the fix this raised KeyError on the missing counters.
+    analytics._record_query("hello world", success=True, cache_hit=False)
+
+    data = analytics._load_analytics()
+    assert data["total_queries"] == 2
+    assert data["successful_queries"] == 1
+    assert data["query_patterns"]["hello world"]["count"] == 1