Delegate review to codex instance (#5572)

In this PR, I am exploring migrating task kind to an invocation of
Codex. The main reason would be getting rid off multiple
`ConversationHistory` state and streamlining our context/history
management.

This approach depends on opening a channel between the sub-codex and
codex. This channel is responsible for forwarding `interactive`
(`approvals`) and `non-interactive` events. The `task` is responsible
for handling those events.

This opens the door for implementing `codex as a tool`, replacing
`compact` and `review`, and potentially subagents.

One consideration is this code is very similar to `app-server` specially
in the approval part. If in the future we wanted an interactive
`sub-codex` we should consider using `codex-mcp`

codex-rs/core/src/features.rs

@@ -122,8 +122,9 @@ impl Features {
         self.enabled.insert(f);
     }
 
-    pub fn disable(&mut self, f: Feature) {
+    pub fn disable(&mut self, f: Feature) -> &mut Self {
         self.enabled.remove(&f);
+        self
     }
 
     pub fn record_legacy_usage_force(&mut self, alias: &str, feature: Feature) {