Fix missing workspace when herald run in container

crates/herald-server/src/sandbox/tools.rs

@@ -41,6 +41,19 @@ fn review_tools() -> Vec<Tool> {
                 }
             }),
         ),
+        Tool::new(
+            "file_size",
+            "Get the size of a file inside the repository in bytes.",
+            json!({
+                "type": "object",
+                "properties": {
+                    "path": {
+                        "type": "string",
+                        "description": "File path relative to the repository root."
+                    }
+                }
+            }),
+        ),
         Tool::new(
             "read_file",
             "Read the content of a text file inside the repository. Every line is \
@@ -111,12 +124,19 @@ pub async fn dispatch(sandbox: &Sandbox, name: &str, args: &Value) -> anyhow::Re
     match name {
         "ls" => ls(sandbox, args).await,
         "read_file" => read_file(sandbox, args).await,
+        "file_size" => file_size(sandbox, args).await,
         "grep" => grep(sandbox, args).await,
         "find" => find(sandbox, args).await,
         other => bail!("unknown tool `{other}`"),
     }
 }
 
+async fn file_size(sandbox: &Sandbox, args: &Value) -> anyhow::Result<String> {
+    let path = resolve(sandbox, required_str(args, "path")?)?;
+    let size = sandbox.exec(&["du", "-b", "--", &path]).await?;
+    into_stdout(size)
+}
+
 async fn ls(sandbox: &Sandbox, args: &Value) -> anyhow::Result<String> {
     let path = resolve(sandbox, optional_str(args, "path").unwrap_or("."))?;
     let output = sandbox.exec(&["ls", "-la", "--", &path]).await?;