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/conversation_manager.rs

@@ -73,7 +73,7 @@ impl ConversationManager {
             config,
             auth_manager,
             InitialHistory::New,
-            self.session_source,
+            self.session_source.clone(),
         )
         .await?;
         self.finalize_spawn(codex, conversation_id).await
@@ -145,7 +145,13 @@ impl ConversationManager {
         let CodexSpawnOk {
             codex,
             conversation_id,
-        } = Codex::spawn(config, auth_manager, initial_history, self.session_source).await?;
+        } = Codex::spawn(
+            config,
+            auth_manager,
+            initial_history,
+            self.session_source.clone(),
+        )
+        .await?;
         self.finalize_spawn(codex, conversation_id).await
     }
 
@@ -179,7 +185,7 @@ impl ConversationManager {
         let CodexSpawnOk {
             codex,
             conversation_id,
-        } = Codex::spawn(config, auth_manager, history, self.session_source).await?;
+        } = Codex::spawn(config, auth_manager, history, self.session_source.clone()).await?;
 
         self.finalize_spawn(codex, conversation_id).await
     }