fix: document ctx_execute_file workspace boundary

extensions/tool-routing.ts

@@ -36,6 +36,12 @@ export function buildToolRoutingSection(selectedTools: SelectedTools): string {
 		);
 	}
 
+	if (hasTool(selectedTools, "ctx_execute_file")) {
+		rules.push(
+			"- ctx_execute_file is confined to the current project root. Do not call it for absolute paths outside the workspace, ../ traversal, or symlinks that resolve outside the workspace; host permission approval does not bypass this Context Mode boundary. Use another explicitly authorized tool for those files.",
+		);
+	}
+
 	if (hasTool(selectedTools, "read")) {
 		rules.push(
 			"- Use read directly when exact text is needed for editing or when a file is small. Do not read a complete large file merely to copy, compare, hash, count, or summarize it.",