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/protocol/src/protocol.rs

@@ -950,7 +950,7 @@ impl InitialHistory {
     }
 }
 
-#[derive(Serialize, Deserialize, Copy, Clone, Debug, PartialEq, Eq, JsonSchema, TS, Default)]
+#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq, JsonSchema, TS, Default)]
 #[serde(rename_all = "lowercase")]
 #[ts(rename_all = "lowercase")]
 pub enum SessionSource {
@@ -959,10 +959,18 @@ pub enum SessionSource {
     VSCode,
     Exec,
     Mcp,
+    SubAgent(SubAgentSource),
     #[serde(other)]
     Unknown,
 }
 
+#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq, JsonSchema, TS)]
+pub enum SubAgentSource {
+    Review,
+    Compact,
+    Other(String),
+}
+
 #[derive(Serialize, Deserialize, Clone, Debug, JsonSchema, TS)]
 #[ts(optional_fields = nullable)]
 pub struct SessionMeta {