feat(client): reloadAuth() wrapper

Studio + pilot apps can now trigger a hub-side TokenStore
swap without restarting the daemon:

  await client.reloadAuth();  // returns new token count

Throws when the new config is invalid; the existing store
stays in place server-side so a botched rotation can't lock
the operator out.

Bindings regenerated for the new
HubAdmin.ReloadAuth + ReloadAuthResponse + LoggedEvent
.caller_name proto additions.

dart analyze clean; dart test green (4 tests).

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/src/hub_client.dart

@@ -188,6 +188,18 @@ class HubClient {
     );
   }
 
+  /// Re-read `auth.tokens:` from operator config + env vars
+  /// and atomically swap the hub's live token store. Used by
+  /// operators to rotate tokens without restarting the daemon.
+  /// Returns the new token count after the swap. Throws when
+  /// the new config is invalid; the existing store stays in
+  /// place in that case so a botched rotation can't lock the
+  /// operator out.
+  Future<int> reloadAuth() async {
+    final r = await _admin.reloadAuth(Empty());
+    return r.tokenCount;
+  }
+
   /// Server-streaming audit-log subscription. The hub first
   /// replays up to [backfill] historical events (oldest-last so
   /// the receiver sees them in chronological order), then keeps