feat: ephemeral threads (#9765)

Add ephemeral threads capabilities. Only exposed through the
`app-server` v2

The idea is to disable the rollout recorder for those threads.

codex-rs/core/src/codex_thread.rs

@@ -4,18 +4,35 @@ use crate::error::Result as CodexResult;
 use crate::protocol::Event;
 use crate::protocol::Op;
 use crate::protocol::Submission;
+use codex_protocol::config_types::Personality;
+use codex_protocol::openai_models::ReasoningEffort;
+use codex_protocol::protocol::AskForApproval;
+use codex_protocol::protocol::SandboxPolicy;
+use codex_protocol::protocol::SessionSource;
 use std::path::PathBuf;
 use tokio::sync::watch;
 
+#[derive(Clone, Debug)]
+pub struct ThreadConfigSnapshot {
+    pub model: String,
+    pub model_provider_id: String,
+    pub approval_policy: AskForApproval,
+    pub sandbox_policy: SandboxPolicy,
+    pub cwd: PathBuf,
+    pub reasoning_effort: Option<ReasoningEffort>,
+    pub personality: Option<Personality>,
+    pub session_source: SessionSource,
+}
+
 pub struct CodexThread {
     codex: Codex,
-    rollout_path: PathBuf,
+    rollout_path: Option<PathBuf>,
 }
 
 /// Conduit for the bidirectional stream of messages that compose a thread
 /// (formerly called a conversation) in Codex.
 impl CodexThread {
-    pub(crate) fn new(codex: Codex, rollout_path: PathBuf) -> Self {
+    pub(crate) fn new(codex: Codex, rollout_path: Option<PathBuf>) -> Self {
         Self {
             codex,
             rollout_path,
@@ -43,7 +60,11 @@ impl CodexThread {
         self.codex.agent_status.clone()
     }
 
-    pub fn rollout_path(&self) -> PathBuf {
+    pub fn rollout_path(&self) -> Option<PathBuf> {
         self.rollout_path.clone()
     }
+
+    pub async fn config_snapshot(&self) -> ThreadConfigSnapshot {
+        self.codex.thread_config_snapshot().await
+    }
 }