phase 2 removing tbc

Strip dead pfUI.client > 11200 and pfUI.expansion == "tbc" branches now
that vanilla is the only supported client.

- pfUI.lua: hardcode expansion = "vanilla"; collapse force_region matrix
- compat/vanilla.lua, libs/{libcast,libdebuff,libtotem,libunitscan,
  focus}: drop always-false early-returns
- api/unitframes.lua: delete TargetBuffOnUpdate poller + tbc visibility
  and secure-template branches; click-cast keeps only vanilla path
- api/ui-widgets.lua: unconditional EffectiveScale divide
- env/tables.lua: drop unused focus/focustarget pfValidUnits entries
- modules/actionbar.lua: simplify EnablePaging, drop ButtonSwitch/
  petvisibility, unwrap prowl block, single keybind-remap path
- modules/{castbar,chat,cooldown,loot,questitem,totems}: unwrap
  always-true conditionals
- modules/nameplates.lua: cfg-only fake-cooldown gate, unwrap overlap/
  clickthrough + mouselook blocks
- modules/friends.lua + skins/blizzard/friends.lua: maxtab = 4
- skins/blizzard/{help,game_menu,questlog}: drop tbc-only branches

modules/chat.lua

@@ -3,17 +3,15 @@ pfUI:RegisterModule("chat", "vanilla:tbc", function ()
   local panelfont_size = C.panel.use_unitfonts == "1" and C.global.font_unit_size or C.global.font_size
   local rawborder, default_border = GetBorderSize("chat")
 
-  if pfUI.client <= 11200 then
-    -- The 'GetChatWindowInfo' function returns shown as 'false' while the UIParent is hidden (Alt+Z).
-    -- Based on that return value, the 'FloatingChatFrame_Update' would remove every chat frame,
-    -- that isn't tabbed while the interface is hidden. With this hook we prevent the original
-    -- 'FloatingChatFrame_Update' function from being called during that time.
+  -- The 'GetChatWindowInfo' function returns shown as 'false' while the UIParent is hidden (Alt+Z).
+  -- Based on that return value, the 'FloatingChatFrame_Update' would remove every chat frame,
+  -- that isn't tabbed while the interface is hidden. With this hook we prevent the original
+  -- 'FloatingChatFrame_Update' function from being called during that time.
 
-    local HookFloatingChatFrame_Update = _G.FloatingChatFrame_Update
-    _G.FloatingChatFrame_Update = function(id, onUpdateEvent)
-      if not UIParent:IsShown() then return end
-      HookFloatingChatFrame_Update(id, onUpdateEvent)
-    end
+  local HookFloatingChatFrame_Update = _G.FloatingChatFrame_Update
+  _G.FloatingChatFrame_Update = function(id, onUpdateEvent)
+    if not UIParent:IsShown() then return end
+    HookFloatingChatFrame_Update(id, onUpdateEvent)
   end
 
   _G.CHAT_FONT_HEIGHTS = { 8, 10, 12, 14, 16, 18, 20 }