fix: taking plan type from usage endpoint instead of thru auth token (#7610)

pull plan type from the usage endpoint, persist it in session state /
tui state, and propagate through rate limit snapshots

codex-rs/codex-api/src/rate_limits.rs

@@ -37,6 +37,7 @@ pub fn parse_rate_limit(headers: &HeaderMap) -> Option<RateLimitSnapshot> {
         primary,
         secondary,
         credits,
+        plan_type: None,
     })
 }