feat(app-server): enforce managed remote control disable (#27961)

## Why

Managed deployments need a reliable deny gate for remote control.
Persisted enablement and explicit startup requests currently remain able
to start the transport, while the removed `features.remote_control` key
is intentionally only a compatibility no-op.

This adds a dedicated requirement that administrators can use to force
remote control off without deleting the user's persisted preference.
Removing the requirement and restarting restores the prior choice.

## What Changed

- Added top-level `allow_remote_control` requirements parsing, sourced
layer precedence, debug output, and `configRequirements/read` exposure
as `allowRemoteControl`.
- Added a typed transport policy captured from the startup requirements
snapshot. Managed disable forces the initial state to disabled and
prevents enrollment, refresh, connection, and persisted-preference
mutation.
- Rejected every `remoteControl/*` RPC before parameter deserialization
with JSON-RPC `-32600` and `remote control is disabled by managed
requirements`.
- Preserved the existing disabled status notification and the previous
behavior when the requirement is `true` or omitted.
- Regenerated app-server protocol schemas and documented the new
requirement.

## Verification

- Confirmed all remote-control RPCs, including a malformed request,
return the managed-policy error while the initial status notification
remains `disabled`.
- Confirmed explicit ephemeral startup and persisted enablement make no
backend connection and leave the SQLite preference unchanged.
- Confirmed `allow_remote_control = true` does not enable or block
remote control and `configRequirements/read` returns
`allowRemoteControl: false` for the deny policy.

Related issue: N/A (managed-policy hardening).

codex-rs/core/src/config/config_tests.rs

@@ -8304,6 +8304,7 @@ async fn test_requirements_web_search_mode_allowlist_does_not_warn_when_unset()
         allowed_web_search_modes: Some(vec![codex_config::WebSearchModeRequirement::Cached]),
         allow_managed_hooks_only: None,
         allow_appshots: None,
+        allow_remote_control: None,
         computer_use: None,
         windows: None,
         feature_requirements: None,

codex-rs/core/src/config/mod.rs

@@ -2631,6 +2631,7 @@ impl Config {
             web_search_mode: mut constrained_web_search_mode,
             allow_managed_hooks_only: _,
             allow_appshots: _,
+            allow_remote_control: _,
             computer_use: _,
             feature_requirements,
             managed_hooks: _,