feat: add exec pathPrepend config

src/config/types.tools.ts

@@ -129,6 +129,8 @@ export type ExecToolConfig = {
   ask?: "off" | "on-miss" | "always";
   /** Default node binding for exec.host=node (node id/name). */
   node?: string;
+  /** Directories to prepend to PATH when running exec (gateway/sandbox). */
+  pathPrepend?: string[];
   /** Default time (ms) before an exec command auto-backgrounds. */
   backgroundMs?: number;
   /** Default timeout (seconds) before auto-killing exec commands. */