**fix(executor, auth): ensure index assignment consistency for auth objects**

- Updated `usage_helpers.go` to call `EnsureIndex()` for proper index assignment in reporter initialization.
- Adjusted `auth/manager.go` to assign auth indices inside a locked section when they are unassigned, ensuring thread safety and consistency.

internal/runtime/executor/usage_helpers.go

@@ -37,7 +37,7 @@ func newUsageReporter(ctx context.Context, provider, model string, auth *cliprox
 	}
 	if auth != nil {
 		reporter.authID = auth.ID
-		reporter.authIndex = auth.Index
+		reporter.authIndex = auth.EnsureIndex()
 	}
 	return reporter
 }