[client] Tune retries and backoff (#1956)

## Summary
10 is a bit excessive 😅 Also updates our backoff factor to space out
requests further.

codex-rs/core/src/model_provider_info.rs

@@ -15,7 +15,7 @@ use std::time::Duration;
 
 use crate::error::EnvVarError;
 const DEFAULT_STREAM_IDLE_TIMEOUT_MS: u64 = 300_000;
-const DEFAULT_STREAM_MAX_RETRIES: u64 = 10;
+const DEFAULT_STREAM_MAX_RETRIES: u64 = 5;
 const DEFAULT_REQUEST_MAX_RETRIES: u64 = 4;
 
 /// Wire protocol that the provider speaks. Most third-party services only

codex-rs/core/src/util.rs

@@ -7,7 +7,7 @@ use tokio::sync::Notify;
 use tracing::debug;
 
 const INITIAL_DELAY_MS: u64 = 200;
-const BACKOFF_FACTOR: f64 = 1.3;
+const BACKOFF_FACTOR: f64 = 2.0;
 
 /// Make a CancellationToken that is fulfilled when SIGINT occurs.
 pub fn notify_on_sigint() -> Arc<Notify> {