fix(niri): reconnect IPC and stop per-event throttling to prevent freeze

The niri IPC worker slept 1ms per event and never reconnected. Under an
event burst the per-event cap back-pressures the socket, niri fills its
send buffer and drops the stream; read_line then returns false, the
detached thread exits and the module freezes permanently.

Remove the per-event sleep so events drain as fast as they arrive, and
wrap the socket setup and read loop in a reconnect loop that backs off
and re-establishes the stream on drop. A running_ flag lets the thread
exit cleanly on teardown.

Fixes #5117.

include/modules/niri/backend.hpp

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <atomic>
 #include <list>
 #include <mutex>
 #include <string>
@@ -18,6 +19,7 @@ class EventHandler {
 class IPC {
  public:
   IPC();
+  ~IPC();
 
   void registerForIPC(const std::string& ev, EventHandler* ev_handler);
   void unregisterForIPC(EventHandler* handler);
@@ -45,6 +47,8 @@ class IPC {
   util::JsonParser parser_;
   std::mutex callbackMutex_;
   std::list<std::pair<std::string, EventHandler*>> callbacks_;
+
+  std::atomic<bool> running_{true};
 };
 
 inline std::unique_ptr<IPC> gIPC;