Initialize cwd in TUI resume and fork test fixtures (#43419)

Set `SessionTarget::cwd` to `None` in the remote resume permission-override
and CLI fork startup tests to match the struct's required fields.

GitOrigin-RevId: d1e7a2e6b7ae3dda17ef062984917861c12fdeff

codex-rs/tui/src/app/tests.rs

@@ -3094,6 +3094,7 @@ async fn remote_resume_rejects_explicit_permission_override() -> Result<()> {
         SessionTarget {
             thread_id: ThreadId::new(),
             path: None,
+            cwd: None,
             history_mode: None,
         },
     )

codex-rs/tui/src/app/tests/startup_defaults_tests.rs

@@ -107,6 +107,7 @@ async fn cli_fork_omits_implicit_model_and_effort() -> Result<()> {
         SessionSelection::Fork(crate::resume_picker::SessionTarget {
             path: None,
             thread_id: source,
+            cwd: None,
             history_mode: None,
         }),
     ));