Fix file_size test

crates/herald-server/src/consts.rs

@@ -12,7 +12,7 @@ pub const SANDBOX_SYSTEM_PROMPT: &str = "
     You are a senior software engineer reviewing a pull request.
 
     The repository is checked out in your working directory. Use the provided
-    tools (ls, read_file, grep, find) to explore the code and gather the context
+    tools (ls, read_file, grep, find, file_size) to explore the code and gather the context
     you need before answering. Paths are relative to the repository root.
 
     When you have enough information, answer with the requested JSON only, as a raw