Keep remote workspace roots under server control (#46494)

## Why

Workspace paths from the client configuration belong to the client host. Sending them to a remote app server can override the server's workspace roots.

## What changed

- Omit client-configured `runtimeWorkspaceRoots` from remote start, resume, and fork requests so the server resolves defaults or restores saved roots.
- Preserve server-provided roots when forking an active session or side conversation, including after reloading client configuration.
- Reject `--add-dir` and `sandbox_workspace_write.writable_roots` command-line overrides with `--remote` before connecting, directing users to configure additional roots on the server.

## Testing

Add regression coverage for remote workspace roots across start, turn, resume, and fork operations; active-session forks after configuration reloads; and embedded requests retaining explicit roots. CLI tests cover rejected root overrides and continued acceptance of network-access overrides.

GitOrigin-RevId: b87ea6037d197db68e25a1a8610d693f6aa13caf

codex-rs/cli/tests/features.rs

@@ -299,6 +299,61 @@ async fn features_list_honors_cloud_managed_feature_requirements() -> Result<()>
     Ok(())
 }
 
+#[test]
+fn remote_start_rejects_add_dir_before_connecting() -> Result<()> {
+    let home = TempDir::new()?;
+    let output = codex_command(home.path())?
+        .env("TERM", "xterm-256color")
+        .args(["--remote", "ws://127.0.0.1:1", "--add-dir", "remote-extra"])
+        .assert()
+        .failure()
+        .get_output()
+        .stderr
+        .clone();
+    insta::assert_snapshot!(String::from_utf8(output)?);
+    Ok(())
+}
+
+#[test]
+fn remote_start_rejects_writable_root_overrides_before_connecting() -> Result<()> {
+    for config_override in [
+        "sandbox_workspace_write.writable_roots=[\"./extra\"]",
+        "sandbox_workspace_write={writable_roots=[\"./extra\"],network_access=true}",
+    ] {
+        let home = TempDir::new()?;
+        let output = codex_command(home.path())?
+            .env("TERM", "xterm-256color")
+            .args(["--remote", "ws://127.0.0.1:1", "-c", config_override])
+            .assert()
+            .failure()
+            .get_output()
+            .stderr
+            .clone();
+        let output = String::from_utf8(output)?;
+        insta::allow_duplicates! {
+            insta::assert_snapshot!(output, @"Error: sandbox_workspace_write.writable_roots overrides are not supported with --remote. Configure additional workspace roots on the server.");
+        }
+    }
+    Ok(())
+}
+
+#[test]
+fn remote_start_allows_network_access_overrides_before_requiring_terminal() -> Result<()> {
+    for config_override in [
+        "sandbox_workspace_write.network_access=true",
+        "sandbox_workspace_write={network_access=true}",
+    ] {
+        let home = TempDir::new()?;
+        codex_command(home.path())?
+            .env("TERM", "xterm-256color")
+            .args(["--remote", "ws://127.0.0.1:1", "-c", config_override])
+            .assert()
+            .failure()
+            .stderr(contains("stdin is not a terminal"));
+    }
+    Ok(())
+}
+
 #[test]
 fn no_daemon_rejects_agents_and_explicit_remote_targets() -> Result<()> {
     for args in [

codex-rs/cli/tests/snapshots/features__remote_start_rejects_add_dir_before_connecting.snap

@@ -0,0 +1,5 @@
+---
+source: cli/tests/features.rs
+expression: "String::from_utf8(output)?"
+---
+Error: --add-dir is not supported with --remote. Configure additional workspace roots on the server.