Refactor config loading to use filesystem abstraction (#18209)

Initial pass propagating FileSystem through config loading.

codex-rs/tui/src/onboarding/onboarding_screen.rs

@@ -4,6 +4,7 @@ use crate::legacy_core::windows_sandbox::WindowsSandboxLevelExt;
 use codex_app_server_client::AppServerEvent;
 use codex_app_server_client::AppServerRequestHandle;
 use codex_app_server_protocol::ServerNotification;
+use codex_exec_server::LOCAL_FS;
 use codex_git_utils::resolve_root_git_project_for_trust;
 #[cfg(target_os = "windows")]
 use codex_protocol::config_types::WindowsSandboxLevel;
@@ -123,8 +124,9 @@ impl OnboardingScreen {
         let show_windows_create_sandbox_hint = false;
         let highlighted = TrustDirectorySelection::Trust;
         if show_trust_screen {
-            let trust_target = resolve_root_git_project_for_trust(&cwd)
+            let trust_target = resolve_root_git_project_for_trust(LOCAL_FS.as_ref(), &config.cwd)
                 .await
+                .map(Into::into)
                 .unwrap_or_else(|| cwd.clone());
             steps.push(Step::TrustDirectory(TrustDirectoryWidget {
                 cwd,