nameplates: source totem icons from UnitCreatedBySpell

Read the totem's icon from the totem-drop spell (UnitCreatedBySpell +
GetSpellTexture) instead of the self-aura at index 1 plus a
UNIT_SPELLCAST_SUCCEEDED capture for active totems. The drop spell is a
broadcast descriptor field present for every summoned unit in range, so
it resolves immediately for passive and active totems alike and gives the
totem's own icon rather than the attack-spell proxy. Drops the
UNIT_SPELLCAST_SUCCEEDED registration and handler.

Re-read the spell each render and key the cached texture on the spell id
so an in-place totem swap (same unit, new drop spell -- no plate re-add)
refreshes the icon without needing the plate to leave and re-enter view.

modules/nameplates.lua

@@ -296,18 +296,23 @@ pfUI:RegisterModule("nameplates", function ()
     return plate.creatureType
   end
 
-  -- Totem icon, read straight from the game:
-  --   * Passive totems self-cast their provided buff, so they carry exactly one
-  --     aura whose icon IS the totem's icon (Totem::Summon TOTEM_PASSIVE).
-  --   * Active totems (Searing/Magma/Fire Nova) cast at enemies and hold no
-  --     self-aura, so their icon arrives via UNIT_SPELLCAST_SUCCEEDED (cached
-  --     into plate.totemIcon by the event handler); nil here until then.
+  -- Totem icon: UnitCreatedBySpell returns the totem-drop spell, whose icon IS
+  -- the totem's icon. It's a broadcast descriptor field the client has for every
+  -- summoned unit in range, so it resolves immediately for passive and active
+  -- totems alike -- no self-aura read or attack-cast capture needed.
+  --
+  -- Re-read the spell every call rather than caching the icon outright: a shaman
+  -- can swap the totem in place (same unit, new drop spell) with no plate re-add
+  -- to invalidate a cache, so key the cached texture on the spell id and refresh
+  -- it only when the spell changes.
   local function TotemPlate(plate)
     if C.nameplates.totemicons ~= "1" then return nil end
     if CreatureType(plate) ~= 11 then return nil end
-    if plate.totemIcon then return plate.totemIcon end
-    local aura = C_UnitAuras.GetBuffDataByIndex(plate.cachedGuid, 1)
-    if aura then plate.totemIcon = aura.icon end
+    local spellId = UnitCreatedBySpell(plate.cachedGuid)
+    if spellId ~= plate.totemSpell then
+      plate.totemSpell = spellId
+      plate.totemIcon = spellId and C_Spell.GetSpellTexture(spellId) or nil
+    end
     return plate.totemIcon
   end
 
@@ -499,7 +504,6 @@ nameplates:RegisterEvent("UNIT_SPELLCAST_START")
 nameplates:RegisterEvent("UNIT_SPELLCAST_CHANNEL_START")
 nameplates:RegisterEvent("UNIT_SPELLCAST_STOP")
 nameplates:RegisterEvent("UNIT_SPELLCAST_CHANNEL_STOP")
-nameplates:RegisterEvent("UNIT_SPELLCAST_SUCCEEDED")
 nameplates:RegisterEvent("PLAYER_GUILD_UPDATE")
   
   nameplates:SetScript("OnEvent", function()
@@ -588,6 +592,7 @@ nameplates:RegisterEvent("PLAYER_GUILD_UPDATE")
         plate.nameplate.unit = arg1
         plate.nameplate.creatureType = nil  -- recompute for the new unit
         plate.nameplate.totemIcon = nil
+        plate.nameplate.totemSpell = nil
         if guid then
           plateByGuid[guid] = plate.nameplate
           -- Seed: the unit may already be mid-cast (its UNIT_SPELLCAST_START
@@ -665,22 +670,6 @@ nameplates:RegisterEvent("PLAYER_GUILD_UPDATE")
         end
       end
 
-    elseif event == "UNIT_SPELLCAST_SUCCEEDED" then
-      -- Active totems (Searing/Magma/Fire Nova) carry no self-aura, so their
-      -- attack cast is the only icon source. Capture it once per totem, gated on
-      -- creature type so a normal caster's spell never styles it as a totem.
-      if arg1 and strfind(arg1, "^nameplate") then
-        local guid = UnitGUID(arg1)
-        local plate = guid and plateByGuid[guid]
-        if plate and not plate.totemIcon and arg3 and CreatureType(plate) == 11 then
-          local tex = C_Spell.GetSpellTexture(arg3)
-          if tex then
-            plate.totemIcon = tex
-            plate.castUpdate = true  -- re-render now so the icon shows
-          end
-        end
-      end
-
     elseif event == "UNIT_AURA" then
       -- ClassicAPI: fires with arg1 == "nameplateN" when a unit's aura set
       -- changes (add/remove/modify). Flag the matching plate so OnUpdate does a
@@ -1110,7 +1099,7 @@ nameplates:RegisterEvent("PLAYER_GUILD_UPDATE")
     local TotemIcon = TotemPlate(plate)
 
     if TotemIcon then
-      -- icon resolved from the totem's aura / attack cast (already a full path)
+      -- icon resolved from the totem-drop spell (already a full path)
       plate.totem.icon:SetTexture(TotemIcon)
 
       plate.glow:Hide()