hyprland/backend: throw runtime_error instead of log

Allows us to disable modules entirely when socket connection isn't
working. This is similar to how sway handles their socket connections
disabling modules. This supports a single waybar config for multiple
IPCs.

test/hyprland/backend.cpp

@@ -52,10 +52,8 @@ TEST_CASE_METHOD(IPCTestFixture, "XDGRuntimeDirExistsNoHyprDir", "[getSocketFold
   REQUIRE(actualPath == expectedPath);
 }
 
-TEST_CASE_METHOD(IPCMock, "getSocket1JsonReply handles empty response", "[getSocket1JsonReply]") {
+TEST_CASE_METHOD(IPCTestFixture, "getSocket1Reply throws on no socket", "[getSocket1Reply]") {
   std::string request = "test_request";
 
-  Json::Value jsonResponse = getSocket1JsonReply(request);
-
-  REQUIRE(jsonResponse.isNull());
+  CHECK_THROWS(getSocket1Reply(request));
 }

test/hyprland/fixtures/IPCTestFixture.hpp

@@ -19,4 +19,7 @@ class IPCMock : public IPCTestFixture {
  public:
   // Mock getSocket1Reply to return an empty string
   static std::string getSocket1Reply(const std::string& rq) { return ""; }
+
+ protected:
+  const char* instanceSig = "instance_sig";
 };