Stop disabled buttons taking the hover border colour

S:HandleButton ends with an unconditional OnEnter/OnLeave pair that swaps
the border to the value colour and back, and neither handler looks at
IsEnabled. A disabled button still fires both scripts on this client, so
the greyed Activate button, Save changes with nothing pending and Purchase
with nothing selected all lit up under the cursor and read as clickable.

HookScript can't be undone, but handlers fire in registration order, so a
hook registered after HandleButton runs last and has the final say on the
colour. Skin:Button wraps HandleButton with that hook, and every call site
in the plugin now goes through it, so the correction is inherited rather
than repeated per module.

The Activate button carries the border from its own update as well:
activating a spec disables it under the very cursor that just clicked it,
and OnEnter has been and gone by then, so nothing else would put the border
back until the pointer moved off.

Skin:IsEnabled hoists the 0/1-to-boolean normalisation this client needs
out of UpdateActivateState, which held the only copy of it.

Modules/TalentFrame.lua

@@ -56,7 +56,7 @@ function SkinChildren(frame, depth)
 				-- "...MenuClose", and it was coming out of the walk as an
 				-- ordinary templated square with the X stripped off it.
 				if not (name and name:find("Close")) then
-					S:HandleButton(child)
+					Skin:Button(child)
 				end
 			elseif objType == "Frame" then
 				if IsDropDown(child, name) then
@@ -353,17 +353,21 @@ local ACTIVATE_DISABLED_COLOR = {0.55, 0.55, 0.55}
 -- says so -- the ElvUI panel is drawn the same either way. The label is greyed
 -- instead, which is how ElvUI marks a dead button everywhere else.
 --
--- IsEnabled hands back 0 and 1 on this client rather than false and true
--- (probed), and 0 is truthy in Lua, so it's normalised before it's compared
--- against the cached value. Compared rather than written blind because this
--- runs from the button's update: there's no event for a spec becoming active.
+-- The enabled state is compared against the cached one rather than written
+-- blind because this runs from the button's update: there's no event for a spec
+-- becoming active. Skin:IsEnabled does the 0/1-to-boolean normalisation this
+-- client needs (see Skinning.lua).
 local function UpdateActivateState(button)
-	local state = button:IsEnabled()
-	local enabled = state ~= nil and state ~= false and state ~= 0
+	local enabled = Skin:IsEnabled(button)
 
 	if enabled == button.CoAActivateEnabled then return end
 	button.CoAActivateEnabled = enabled
 
+	-- Activating a spec disables this button under the very cursor that just
+	-- clicked it, so its hover border would stay lit until the pointer moved
+	-- off. This update already watches the state, so it carries the border too.
+	Skin:RefreshButtonBorder(button)
+
 	local text = ActivateLabel(button)
 	if not text then return end
 
@@ -380,7 +384,7 @@ local function SkinActivateButton(button)
 		button.CoASkinned = true
 
 		Skin:StripArtByFile(button, Skin.RedButtonArt)
-		S:HandleButton(button)
+		Skin:Button(button)
 
 		button:HookScript("OnUpdate", UpdateActivateState)
 	end
@@ -601,7 +605,7 @@ local function SkinBottomBar()
 		-- stopped at the arrow, and the dead space to its right is taken out
 		-- of the hit rect so it can't swallow clicks meant for those icons.
 		if dropdown and arrow then
-			S:HandleButton(dropdown, nil, nil, true)
+			Skin:Button(dropdown, nil, nil, true)
 
 			if dropdown.backdrop then
 				dropdown.backdrop:ClearAllPoints()
@@ -719,7 +723,7 @@ local function SkinSpecChoices()
 		local cardName = SPEC_CHOICE:format(i)
 		if not _G[cardName] then break end
 
-		S:HandleButton(_G[cardName.."SelectButton"], true)
+		Skin:Button(_G[cardName.."SelectButton"], true)
 	end
 end