fix: remove unused _writableRoots arg to exec() function (#762)

I suspect this was done originally so that `execForSandbox()` had a
consistent signature for both the `SandboxType.NONE` and
`SandboxType.MACOS_SEATBELT` cases, but that is not really necessary and
turns out to make the upcoming Landlock support a bit more complicated
to implement, so I had Codex remove it and clean up the call sites.

codex-cli/tests/cancel-exec.test.ts

@@ -14,7 +14,7 @@ describe("exec cancellation", () => {
     const cmd = ["node", "-e", "setTimeout(() => console.log('late'), 5000);"];
 
     const start = Date.now();
-    const promise = rawExec(cmd, {}, [], abortController.signal);
+    const promise = rawExec(cmd, {}, abortController.signal);
 
     // Abort almost immediately.
     abortController.abort();
@@ -38,7 +38,7 @@ describe("exec cancellation", () => {
 
     const cmd = ["node", "-e", "console.log('finished')"];
 
-    const result = await rawExec(cmd, {}, [], abortController.signal);
+    const result = await rawExec(cmd, {}, abortController.signal);
 
     expect(result.exitCode).toBe(0);
     expect(result.stdout.trim()).toBe("finished");

codex-cli/tests/invalid-command-handling.test.ts

@@ -10,7 +10,7 @@ describe("rawExec – invalid command handling", () => {
   it("resolves with non‑zero exit code when executable is missing", async () => {
     const cmd = ["definitely-not-a-command-1234567890"];
 
-    const result = await rawExec(cmd, {}, []);
+    const result = await rawExec(cmd, {});
 
     expect(result.exitCode).not.toBe(0);
     expect(result.stderr.length).toBeGreaterThan(0);

codex-cli/tests/raw-exec-process-group.test.ts

@@ -33,7 +33,7 @@ describe("rawExec – abort kills entire process group", () => {
     //  - prints the PID of the `sleep`
     //  - waits for `sleep` to exit
     const { stdout, exitCode } = await (async () => {
-      const p = rawExec(cmd, {}, [], abortController.signal);
+      const p = rawExec(cmd, {}, abortController.signal);
 
       // Give Bash a tiny bit of time to start and print the PID.
       await new Promise((r) => setTimeout(r, 100));