refactor: apply 5-pass audit optimizations across mcp-memory codebase

server/src/handlers/git.rs

@@ -69,7 +69,8 @@ impl McpTool for GetActiveWorktreeContextHandler {
 
                 // Truncate diff output if it's too large to save tokens
                 if diff_output.len() > 10000 {
-                    diff_output.truncate(10000);
+                    let valid_boundary = diff_output.floor_char_boundary(10000);
+                    diff_output.truncate(valid_boundary);
                     diff_output.push_str("\n... [Diff truncated due to size]");
                 }