move cap_sid file into ~/.codex so the sandbox cannot overwrite it (#6798)

The `cap_sid` file contains the IDs of the two custom SIDs that the
Windows sandbox creates/manages to implement read-only and
workspace-write sandbox policies.

It previously lived in `<cwd>/.codex` which means that the sandbox could
write to it, which could degrade the efficacy of the sandbox. This
change moves it to `~/.codex/` (or wherever `CODEX_HOME` points to) so
that it is outside the workspace.

codex-rs/cli/src/debug_sandbox.rs

@@ -155,11 +155,11 @@ async fn run_command_under_sandbox(
                 run_windows_sandbox_capture(
                     policy_str,
                     &sandbox_cwd,
+                    base_dir.as_path(),
                     command_vec,
                     &cwd_clone,
                     env_map,
                     None,
-                    Some(base_dir.as_path()),
                 )
             })
             .await;