Remove import

The old load path in codex-rs/rmcp-client/src/oauth.rs only set expires_in when the stored expiry was in the future:

  // codex-rs/rmcp-client/src/oauth.rs:369-374 (original)
  if let Some(expires_at) = entry.expires_at
      && let Some(seconds) = expires_in_from_timestamp(expires_at)
  {
      let duration = Duration::from_secs(seconds);
      token_response.set_expires_in(Some(&duration));
  }

  And expires_in_from_timestamp returned None for expired tokens:

  // codex-rs/rmcp-client/src/oauth.rs:444-453 (original)
  if expires_at <= now_ms {
      None
  } else {
      Some((expires_at - now_ms) / 1000)
  }

  So when the stored token was already expired, set_expires_in was never called, RMCP saw “no expiry,” and it didn’t auto-refresh on handshake.

codex-rs/rmcp-client/src/oauth.rs

@@ -366,9 +366,8 @@ fn load_oauth_tokens_from_file(server_name: &str, url: &str) -> Result<Option<St
             token_response.set_scopes(Some(scopes.into_iter().map(Scope::new).collect()));
         }
 
-        if let Some(expires_at) = entry.expires_at
-            && let Some(seconds) = expires_in_from_timestamp(expires_at)
-        {
+        if let Some(expires_at) = entry.expires_at {
+            let seconds = expires_in_from_timestamp(expires_at).unwrap_or(0);
             let duration = Duration::from_secs(seconds);
             token_response.set_expires_in(Some(&duration));
         }