feat: enable SQLite WAL mode for all databases (AGI ticket #1) (#153)

src/spark/engine.py

@@ -6,7 +6,8 @@ memory consolidation, and the advisory system.
 
 Usage
 -----
-    from spark.engine import spark_engine
+    from spark.engine import get_spark_engine
+    spark_engine = get_spark_engine()
 
     # Capture a swarm event
     spark_engine.on_task_posted(task_id, description)
@@ -346,14 +347,31 @@ class SparkEngine:
         return spark_eidos.get_predictions(limit=limit)
 
 
-# Module-level singleton — respects SPARK_ENABLED config
-def _create_engine() -> SparkEngine:
-    try:
-        from config import settings
-
-        return SparkEngine(enabled=settings.spark_enabled)
-    except Exception:
-        return SparkEngine(enabled=True)
+# ── Lazy singleton ────────────────────────────────────────────────────────────
+_spark_engine: SparkEngine | None = None
 
 
-spark_engine = _create_engine()
+def get_spark_engine() -> SparkEngine:
+    """Return the module-level SparkEngine, creating it on first access."""
+    global _spark_engine
+    if _spark_engine is None:
+        try:
+            from config import settings
+
+            _spark_engine = SparkEngine(enabled=settings.spark_enabled)
+        except Exception:
+            _spark_engine = SparkEngine(enabled=True)
+    return _spark_engine
+
+
+def reset_spark_engine() -> None:
+    """Reset the singleton for test isolation."""
+    global _spark_engine
+    _spark_engine = None
+
+
+def __getattr__(name: str):
+    """Module-level __getattr__ for lazy backward-compatible access to spark_engine."""
+    if name == "spark_engine":
+        return get_spark_engine()
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")