Fix Codex transcript convergence

server/src/session/driver.rs

@@ -156,6 +156,16 @@ pub enum Event {
     AssistantText {
         delta: String,
     },
+    /// The authoritative text of the assistant message whose deltas immediately
+    /// precede this event.
+    ///
+    /// Some providers stream a provisional rendering and revise it before the
+    /// item completes.  This stays append-only like every other transcript
+    /// correction: readers replace the open message rather than editing an old
+    /// line, and replay therefore reaches the same text as the live stream.
+    AssistantTextFinal {
+        text: String,
+    },
     ToolStart {
         id: String,
         tool: String,