[Core] Temporary Fix for Client-side GCD Prediction Issues

* As the GCD is triggered on the client before anything is actually reported from the server, any function using GCDOffset can potentially flash a short duration incorrect prediction based on the mismatched client state
* Temporarily add a 0.125 second period at the start of the GCD where we do not apply the GCD to OffsetRemains

AethysCore/Misc/ToSort.lua

@@ -113,12 +113,22 @@
     if type( Offset ) == "number" then
       ExpirationTime = ExpirationTime - Offset;
     elseif type( Offset ) == "string" then
+      local CastRemains = Player:CastRemains();
+
+      -- Since the GCD is triggered on the client, add a brief grace period to avoid flickering predictions
+      -- TODO: This should probably be event-driven with CAST_ events controlling if the client-side GCD is ignored
+      -- For now, we just hardcode a period of 1/8th of a second which should work in most cases barring extreme lag
+      local GCDRemains = Player:GCDRemains();
+      if Player:GCD() - GCDRemains < 0.125 then
+        GCDRemains = 0;
+      end
+
       if Offset == "GCDRemains" then
-        ExpirationTime = ExpirationTime - Player:GCDRemains();
+        ExpirationTime = ExpirationTime - GCDRemains;
       elseif Offset == "CastRemains" then
-        ExpirationTime = ExpirationTime - Player:CastRemains();
+        ExpirationTime = ExpirationTime - CastRemains;
       elseif Offset == "Auto" then
-        ExpirationTime = ExpirationTime - mathmax( Player:GCDRemains(), Player:CastRemains() );
+        ExpirationTime = ExpirationTime - mathmax( GCDRemains, CastRemains );
       end
     else
       error( "Invalid Offset." );