fix(memory): memory_search 空查询时默认 min_similarity=0.0 触发表扫描

根因: FTS5 空查询返回 0 条，而 memory_stats 因设 min_similarity=Some(0.0)
走表扫描才正确计数。统一空查询行为。

desktop/src-tauri/src/memory_commands.rs

@@ -158,10 +158,18 @@ pub async fn memory_search(
     // Build search query
     let query = options.query.unwrap_or_default();
 
+    // When query is empty, use min_similarity=0.0 to trigger table scan
+    // (FTS5 requires non-empty query; without this, empty query returns 0 results)
+    let min_similarity = if query.trim().is_empty() {
+        Some(0.0)
+    } else {
+        options.min_importance.map(|i| (i as f32) / 10.0)
+    };
+
     let find_options = zclaw_growth::FindOptions {
         scope,
         limit: options.limit.or(Some(50)),
-        min_similarity: options.min_importance.map(|i| (i as f32) / 10.0),
+        min_similarity,
     };
 
     let entries = zclaw_growth::VikingStorage::find(storage.as_ref(), &query, find_options).await