fix: add more fields to ThreadStartResponse and ThreadResumeResponse (#6847)

This adds the following fields to `ThreadStartResponse` and
`ThreadResumeResponse`:

```rust
    pub model: String,
    pub model_provider: String,
    pub cwd: PathBuf,
    pub approval_policy: AskForApproval,
    pub sandbox: SandboxPolicy,
    pub reasoning_effort: Option<ReasoningEffort>,
```

This is important because these fields are optional in
`ThreadStartParams` and `ThreadResumeParams`, so the caller needs to be
able to determine what values were ultimately used to start/resume the
conversation. (Though note that any of these could be changed later
between turns in the conversation.)

Though to get this information reliably, it must be read from the
internal `SessionConfiguredEvent` that is created in response to the
start of a conversation. Because `SessionConfiguredEvent` (as defined in
`codex-rs/protocol/src/protocol.rs`) did not have all of these fields, a
number of them had to be added as part of this PR.

Because `SessionConfiguredEvent` is referenced in many tests, test
instances of `SessionConfiguredEvent` had to be updated, as well, which
is why this PR touches so many files.

codex-rs/app-server/src/codex_message_processor.rs

@@ -118,6 +118,7 @@ use codex_core::parse_cursor;
 use codex_core::protocol::EventMsg;
 use codex_core::protocol::Op;
 use codex_core::protocol::ReviewRequest;
+use codex_core::protocol::SessionConfiguredEvent;
 use codex_core::read_head_for_summary;
 use codex_feedback::CodexFeedback;
 use codex_login::ServerOptions as LoginServerOptions;
@@ -1313,8 +1314,12 @@ impl CodexMessageProcessor {
 
         match self.conversation_manager.new_conversation(config).await {
             Ok(new_conv) => {
-                let conversation_id = new_conv.conversation_id;
-                let rollout_path = new_conv.session_configured.rollout_path.clone();
+                let NewConversation {
+                    conversation_id,
+                    session_configured,
+                    ..
+                } = new_conv;
+                let rollout_path = session_configured.rollout_path.clone();
                 let fallback_provider = self.config.model_provider_id.as_str();
 
                 // A bit hacky, but the summary contains a lot of useful information for the thread
@@ -1339,8 +1344,22 @@ impl CodexMessageProcessor {
                     }
                 };
 
+                let SessionConfiguredEvent {
+                    model,
+                    model_provider_id,
+                    cwd,
+                    approval_policy,
+                    sandbox_policy,
+                    ..
+                } = session_configured;
                 let response = ThreadStartResponse {
                     thread: thread.clone(),
+                    model,
+                    model_provider: model_provider_id,
+                    cwd,
+                    approval_policy: approval_policy.into(),
+                    sandbox: sandbox_policy.into(),
+                    reasoning_effort: session_configured.reasoning_effort,
                 };
 
                 // Auto-attach a conversation listener when starting a thread.
@@ -1653,7 +1672,15 @@ impl CodexMessageProcessor {
                         return;
                     }
                 };
-                let response = ThreadResumeResponse { thread };
+                let response = ThreadResumeResponse {
+                    thread,
+                    model: session_configured.model,
+                    model_provider: session_configured.model_provider_id,
+                    cwd: session_configured.cwd,
+                    approval_policy: session_configured.approval_policy.into(),
+                    sandbox: session_configured.sandbox_policy.into(),
+                    reasoning_effort: session_configured.reasoning_effort,
+                };
                 self.outgoing.send_response(request_id, response).await;
             }
             Err(err) => {