feat: introduce GetConversationSummary RPC (#5803)

This adds an RPC to the app server to the the `ConversationSummary` via
a rollout path. Now that the VS Code extension supports showing the
Codex UI in an editor panel where the URI of the panel maps to the
rollout file, we need to be able to get the `ConversationSummary` from
the rollout file directly.

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

@@ -147,6 +147,10 @@ client_request_definitions! {
         params: NewConversationParams,
         response: NewConversationResponse,
     },
+    GetConversationSummary {
+        params: GetConversationSummaryParams,
+        response: GetConversationSummaryResponse,
+    },
     /// List recorded Codex conversations (rollouts) with optional pagination and search.
     ListConversations {
         params: ListConversationsParams,
@@ -322,6 +326,18 @@ pub struct ResumeConversationResponse {
     pub initial_messages: Option<Vec<EventMsg>>,
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+pub struct GetConversationSummaryParams {
+    pub rollout_path: PathBuf,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, JsonSchema, TS)]
+#[serde(rename_all = "camelCase")]
+pub struct GetConversationSummaryResponse {
+    pub summary: ConversationSummary,
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Default, JsonSchema, TS)]
 #[serde(rename_all = "camelCase")]
 pub struct ListConversationsParams {