Async methods received without an `id` are silently discarded

Repo: viewer
Labels: bug, protocol

Summary

A method dispatched asynchronously that arrives without an id (i.e. in JSON-RPC notification
form) is logged and dropped. No response, no error object, no side effect.

Evidence

indra/llcorehttp/lljsonrpcws.cpp, processRequest, in the if (is_async) branch:

if (is_notification)
{
    LL_WARNS("JSONRPC") << "Async method " << method
                        << " called as notification; ignoring" << LL_ENDL;
    return;
}

Impact

Affects all 14 methods registered via registerAsyncMethod. The caller receives complete
silence and cannot distinguish this from a hung request. Diagnosing it requires reading viewer
logs.

Proposed fix

Return a JSON-RPC InvalidRequest error (-32600) instead of dropping the message, so the
caller learns the request was rejected.

Notes

Async vs. sync dispatch is an internal implementation detail and is deliberately not
documented in the protocol specification — id is assigned by the JSON-RPC layer rather than by
the caller, so this failure mode should not be reachable by a well-behaved client.

Test plan

• Test steps: