ref: state - 2 (#4229)

Extracting tasks in a module and start abstraction behind a Trait (more
to come on this but each task will be tackled in a dedicated PR)
The goal was to drop the ActiveTask and to have a (potentially) set of
tasks during each turn

codex-rs/core/src/state/session.rs

@@ -4,7 +4,6 @@ use std::collections::HashSet;
 
 use codex_protocol::models::ResponseItem;
 
-use crate::codex::AgentTask;
 use crate::conversation_history::ConversationHistory;
 use crate::protocol::RateLimitSnapshot;
 use crate::protocol::TokenUsage;
@@ -14,7 +13,6 @@ use crate::protocol::TokenUsageInfo;
 #[derive(Default)]
 pub(crate) struct SessionState {
     pub(crate) approved_commands: HashSet<Vec<String>>,
-    pub(crate) current_task: Option<AgentTask>,
     pub(crate) history: ConversationHistory,
     pub(crate) token_info: Option<TokenUsageInfo>,
     pub(crate) latest_rate_limits: Option<RateLimitSnapshot>,