Fix driver.ts TS2769 when passing stdio to execFile

ExecFileOptions doesn't declare stdio (it lives on CommonSpawnOptions),
but execFile forwards the option to spawn() at runtime. Cast through
ExecFileOptions so the stdio-ignore path compiles.

Author: claude

tests/driver/driver.ts

@@ -391,16 +391,16 @@ export abstract class GenericTrunkDriver {
     const { stdin: stdinData, ...fileOpts } = execOptions ?? {};
     // Avoid racing our empty-stdin write against short-lived children (e.g.
     // `foo --version`): when the caller has no stdin payload, give the child
-    // a closed stdin up front so nothing can emit EPIPE later.
-    const stdio: ("ignore" | "pipe")[] = stdinData
-      ? ["pipe", "pipe", "pipe"]
-      : ["ignore", "pipe", "pipe"];
+    // a closed stdin up front so nothing can emit EPIPE later. `stdio` isn't
+    // in the ExecFileOptions type but execFile forwards it to spawn at
+    // runtime, so cast through to keep TS happy.
+    const stdio = stdinData ? "pipe" : (["ignore", "pipe", "pipe"] as const);
     const exec = execFile(bin, args, {
       cwd: this.sandboxPath,
       env: executionEnv(),
-      stdio,
       ...fileOpts,
-    });
+      stdio,
+    } as ExecFileOptions);
     if (stdinData) {
       // Defensively swallow EPIPE if the child still manages to exit first.
       // trunk-ignore(eslint/@typescript-eslint/no-empty-function)