mark Feature::RemoteControl as removed (#22386)

## Why

`remote_control` can appear in `config.toml`, CLI feature overrides, and
the app-server config APIs. Before this PR, app-server startup treated
`config.features.enabled(Feature::RemoteControl)` as the signal to start
remote control ([base
code](https://github.com/openai/codex/blob/5e3ee5eddfa5333f2e0b011880abf0cbf92bd295/codex-rs/app-server/src/lib.rs#L678-L680)).
That meant a user with:

```toml
[features]
remote_control = true
```

would accidentally opt every app-server process into remote control.
Remote-control startup should instead be a per-process launch decision
made by CLI flags.

## What Changed

- Marks `Feature::RemoteControl` as `Stage::Removed`, keeping
`remote_control` as a known compatibility key while making it
config-inert.
- Adds a hidden `--remote-control` process flag to `codex app-server`
and standalone `codex-app-server`.
- Plumbs that flag through
`AppServerRuntimeOptions.remote_control_enabled` and makes app-server
startup use only that runtime option to decide whether to start remote
control.
- Removes the app-server config mutation hook that reloaded config and
toggled remote control at runtime.
- Updates managed daemon spawning to use `codex app-server
--remote-control --listen unix://` instead of `--enable remote_control`.

Config APIs can still list, read, write, and set `remote_control`; those
operations just no longer affect remote-control process enrollment.

codex-rs/cli/src/main.rs

@@ -428,6 +428,10 @@ struct AppServerCommand {
     )]
     listen: codex_app_server::AppServerTransport,
 
+    /// Enable remote control for this app-server process.
+    #[arg(long = "remote-control", hide = true)]
+    remote_control: bool,
+
     /// Controls whether analytics are enabled by default.
     ///
     /// Analytics are disabled by default for app-server. Users have to explicitly opt in
@@ -503,10 +507,10 @@ enum AppServerDaemonSubcommand {
     /// Restart the local app server daemon.
     Restart,
 
-    /// Enable remote_control for future starts and a currently running managed daemon.
+    /// Enable remote control for future starts and a currently running managed daemon.
     EnableRemoteControl,
 
-    /// Disable remote_control for future starts and a currently running managed daemon.
+    /// Disable remote control for future starts and a currently running managed daemon.
     DisableRemoteControl,
 
     /// Stop the local app server daemon.
@@ -529,7 +533,7 @@ struct AppServerProxyCommand {
 
 #[derive(Debug, Args)]
 struct AppServerBootstrapCommand {
-    /// Launch the managed app-server with remote_control enabled.
+    /// Launch the managed app-server with remote control enabled.
     #[arg(long = "remote-control")]
     remote_control: bool,
 }
@@ -888,6 +892,7 @@ async fn cli_main(arg0_paths: Arg0DispatchPaths) -> anyhow::Result<()> {
             let AppServerCommand {
                 subcommand,
                 listen,
+                remote_control,
                 analytics_default_enabled,
             } = app_server_cli;
             reject_remote_mode_for_app_server_subcommand(
@@ -898,13 +903,18 @@ async fn cli_main(arg0_paths: Arg0DispatchPaths) -> anyhow::Result<()> {
             match subcommand {
                 None => {
                     let transport = listen;
-                    codex_app_server::run_main_with_transport(
+                    let runtime_options = codex_app_server::AppServerRuntimeOptions {
+                        remote_control_enabled: remote_control,
+                        ..Default::default()
+                    };
+                    codex_app_server::run_main_with_transport_options(
                         arg0_paths.clone(),
                         root_config_overrides,
                         codex_config::LoaderOverrides::default(),
                         analytics_default_enabled,
                         transport,
                         codex_protocol::protocol::SessionSource::VSCode,
+                        runtime_options,
                     )
                     .await?;
                 }
@@ -2379,6 +2389,7 @@ mod tests {
     fn app_server_analytics_default_disabled_without_flag() {
         let app_server = app_server_from_args(["codex", "app-server"].as_ref());
         assert!(!app_server.analytics_default_enabled);
+        assert!(!app_server.remote_control);
         assert_eq!(
             app_server.listen,
             codex_app_server::AppServerTransport::Stdio