feat: auto compact for hnsw when recompute

docs/configuration-guide.md

@@ -317,7 +317,7 @@ leann search my-index "your query" --no-recompute
 When to use:
 - Extreme low latency requirements (high QPS, interactive assistants)
 - Read-heavy workloads where storage is cheaper than latency
-- Environments without a stable embedding server
+- No always-available GPU
 
 Constraints:
 - HNSW: when `--no-recompute` is set, LEANN automatically disables compact mode during build

packages/leann-core/src/leann/api.py

@@ -162,6 +162,18 @@ class LeannBuilder:
         **backend_kwargs,
     ):
         self.backend_name = backend_name
+        # Normalize incompatible combinations early (for consistent metadata)
+        if backend_name == "hnsw":
+            is_recompute = backend_kwargs.get("is_recompute", True)
+            is_compact = backend_kwargs.get("is_compact", True)
+            if is_recompute is False and is_compact is True:
+                warnings.warn(
+                    "HNSW with is_recompute=False requires non-compact storage. Forcing is_compact=False.",
+                    UserWarning,
+                    stacklevel=2,
+                )
+                backend_kwargs["is_compact"] = False
+
         backend_factory: Optional[LeannBackendFactoryInterface] = BACKEND_REGISTRY.get(backend_name)
         if backend_factory is None:
             raise ValueError(f"Backend '{backend_name}' not found or not registered.")