Replace Mutex with RwLock for ProviderManager and FrecencyStore in the
IPC server. Most request types (Query, Providers, Submenu, PluginAction)
only need read access and can now proceed concurrently. Only Launch
(frecency write) and Refresh (provider write) acquire exclusive locks.
Also adds a warn!() log for malformed JSON requests before sending the
error response, improving observability for debugging client issues.
Provider trait now requires Send + Sync to satisfy RwLock's Sync bound
on the inner type. RuntimeProvider and LuaProvider gain the
corresponding unsafe impl Sync.
vikingowl
3349350bf6