perf(mcp): Batch semantic code search embeddings to resolve CPU bottleneck and fix linting warnings

server/src/handlers/ast.rs

@@ -2,7 +2,7 @@ use crate::router::McpTool;
 use crate::state::MemoryState;
 use crate::tools::ReadFileSkeletonTool;
 use async_trait::async_trait;
-use serde_json::{json, Value};
+use serde_json::Value;
 use std::sync::Arc;
 use tree_sitter::{Parser, Node};