fix(items): grace window for nil-after-occupied without retry polling

GetContainerItemInfo returns nil for some occupied slots during server
lag, causing Bagnon to draw the slot empty. Earlier retry-polling
approach caused massive lag because every legitimately emptied slot
also matched the "previously had item, now nil" condition and ran ~30
live reads over 3s per move.

New approach: on a nil-after-occupied read, if we're within
GRACE_WINDOW (0.5s) of the last good draw, keep the prior draw and
queue ONE re-check at the deadline — no polling. A genuinely emptied
slot resolves at the deadline; a recovered slot redraws with correct
data. lastGoodTime is set only on non-nil reads, so persistent lag
eventually accepts the empty.

Bagnon/components/item.lua

@@ -248,6 +248,38 @@ end
 --[[ Update Methods ]]
 --
 
+-- Lag-race protection for slots that read nil briefly after being occupied.
+-- When this happens we keep the prior draw and schedule ONE re-check at the
+-- grace deadline; we never poll. After the deadline, whatever the live read
+-- says wins, so genuinely emptied slots resolve within GRACE_WINDOW seconds.
+local GRACE_WINDOW = 0.5
+local pendingVerify = {}  -- slot -> deadline (GetTime)
+local verifyFrame = CreateFrame('Frame')
+verifyFrame:Hide()
+verifyFrame:SetScript('OnUpdate', function(self, elapsed)
+	self.tick = (self.tick or 0) + elapsed
+	if self.tick < 0.1 then return end
+	self.tick = 0
+	local now = GetTime()
+	for slot, deadline in pairs(pendingVerify) do
+		if now >= deadline then
+			pendingVerify[slot] = nil
+			if slot:IsVisible() then
+				slot:Update()
+			end
+		end
+	end
+	if not next(pendingVerify) then
+		self:Hide()
+	end
+end)
+
+local function scheduleVerify(slot)
+	if pendingVerify[slot] then return end
+	pendingVerify[slot] = GetTime() + GRACE_WINDOW
+	verifyFrame:Show()
+end
+
 
 -- Update the texture, lock status, and other information about an item
 function ItemSlot:Update()
@@ -255,6 +287,18 @@ function ItemSlot:Update()
 
 	local texture, count, locked, quality, readable, lootable, link = self:GetItemSlotInfo()
 
+	-- If the slot was occupied at our last good draw and the live read just
+	-- returned nil within the grace window, keep the previous draw and queue
+	-- a single re-check. No retry storm.
+	if (not link) and self.hasItem and (self.lastGoodTime or 0) + GRACE_WINDOW > GetTime() then
+		scheduleVerify(self)
+		return
+	end
+
+	if link then
+		self.lastGoodTime = GetTime()
+	end
+
 	self:SetItem(link)
 	self:SetTexture(texture)
 	self:SetCount(count)