fix(app-server): add will_retry to ErrorNotification (#7611)

VSCE renders `codex/event/stream_error` (automatically retried, e.g.
`"Reconnecting... 1/n"`) and `codex/event/error` (terminal errors)
differently, so add `will_retry` on ErrorNotification to indicate this.

codex-rs/app-server-protocol/src/protocol/v2.rs

@@ -942,6 +942,9 @@ pub struct TurnError {
 #[ts(export_to = "v2/")]
 pub struct ErrorNotification {
     pub error: TurnError,
+    // Set to true if the error is transient and the app-server process will automatically retry.
+    // If true, this will not interrupt a turn.
+    pub will_retry: bool,
     pub thread_id: String,
     pub turn_id: String,
 }