refactor(server): Resolve bottlenecks and duplications

- Removed heavy Tantivy index rebuild loop that ran every 5 seconds and rewrote entire graph to disk
- Converted polling worker to lightweight IndexWriter committer
- Fixed 67+ instances of unnecessary clone and string parsing overhead in tool return results
- Deduplicated state graph modification methods

server/src/state.rs

@@ -52,11 +52,7 @@ impl MemoryState {
         self.graph.read()
     }
 
-    pub fn write_to_local_delta<F: FnOnce(&mut KnowledgeGraph)>(&self, update_fn: F) {
-        self.graph.modify(update_fn);
-    }
-
-    pub fn apply_sync_write<F: FnOnce(&mut KnowledgeGraph)>(&self, update_fn: F) {
+    pub fn modify_graph<F: FnOnce(&mut KnowledgeGraph)>(&self, update_fn: F) {
         self.graph.modify(update_fn);
     }