Retire the hasPfUI76 flag and the pfUI 7.6 branches it gated

Assume a modern pfUI, and drop the version-tiered branching entirely: 31 call
sites across five files, plus the flag and its detector.

Note which side was actually dead. HasPfUI76() required four things -- pfUI
version >= 7.6, Nampower >= 2.40, pfUI.libdebuff_objects_guid, and
pfUI.libdebuff_casts. The last one does not exist: pfUI exports 28 libdebuff_*
tables and libdebuff_casts is not among them (libdebuff_recent_casts is a
dedup table keyed [targetGuid][spellName][casterGuid], a different shape). So
the detector returned false at any version, and it was the hasPfUI76-TRUE
branches that never ran, not the fallbacks. Removing those is behaviour-
preserving; keeping SCRM as the owner of castTracking is what the code has
always actually done.

Removed accordingly:
- lib:HasPfUI76(), both flag declarations, and the block that would have aliased
  castTracking to pfUI.libdebuff_casts and re-pointed lib.objects/iconCache.
- HookPfUILibdebuff's "7.6 handles durations internally" early return, so the
  GetDuration/AddEffect hooks below it are visibly the live path again.
- The SPELL_START_OTHER / SPELL_FAILED_OTHER unregister arm, the pfUI branch of
  GetAuraTrackingData, the pfUI76 arm of the libdebuff zone/death cleanup, the
  pfUI backing table in the /cleveroid aura dump, and two status-string suffixes.
- SyncComboDurationToPfUI (77 lines) with its two call sites: it returned
  immediately whenever hasPfUI76, and is inert once the tier split is gone.

Unconditionalised the paths that were gated on `not hasPfUI76`: the castTracking
populate/clear/sweep, InitPfUIIntegration on login, and ten libdebuff duration
lookups.

Verified no hasPfUI76 reference remains, and that per-file block balance is
unchanged from HEAD.

Conditionals.lua

@@ -779,14 +779,6 @@ CleveRoids.DownrankBlocked = CleveRoids.DownrankBlocked or {}
 function CleveRoids.GetAuraTrackingData(targetGuid)
     if not targetGuid then return nil, false end
 
-    -- pfUI path: read directly from pfUI's table (has downrank protection built-in)
-    if CleveRoids.hasPfUI76 and pfUI and pfUI.libdebuff_all_auras then
-        local data = pfUI.libdebuff_all_auras[targetGuid]
-        if data then return data, true end
-        -- Fall through: our table may have test entries even when pfUI is active
-    end
-
-    -- Standalone path (or pfUI had no data for this GUID)
     local data = CleveRoids.AllCasterAuraTracking[targetGuid]
     if data then return data, false end
     return nil, false
@@ -995,7 +987,7 @@ local function OnAutoAttackOther(attackerGuid, targetGuid, totalDamage, hitInfo,
                             end
 
                             -- Sync to pfUI if loaded (pre-7.6 only)
-                            if not CleveRoids.hasPfUI76 and pfUI and pfUI.api and pfUI.api.libdebuff then
+                            if pfUI and pfUI.api and pfUI.api.libdebuff then
                                 local spellName = C_Spell.GetSpellName(spellID) or nil
                                 local baseName = CleveRoids.StripRank(spellName)
                                 local targetName = (lib.guidToName and lib.guidToName[normalizedTarget]) or UnitName("target")
@@ -1175,7 +1167,7 @@ local function OnAuraCastOther(spellId, casterGuid, targetGuid, effect, effectAu
     -- full downrank protection — we read from that table via GetAuraTrackingData().
     if spellId and durationMs and durationMs > 0 then
         local spellName = C_Spell.GetSpellName(spellId)
-        if spellName and not CleveRoids.hasPfUI76 then
+        if spellName then
             CleveRoids._allCasterAuraDirty = true
             if not CleveRoids.AllCasterAuraTracking[targetGuid] then
                 CleveRoids.AllCasterAuraTracking[targetGuid] = {}
@@ -1378,7 +1370,7 @@ autoAttackFrame:SetScript("OnEvent", function()
         if spellId and spellId > 0 and durationMs and durationMs > 0 then
             local playerGUID = CleveRoids.GetGUID("player")
             local durSpellName = C_Spell.GetSpellName(spellId)
-            if playerGUID and durSpellName and not CleveRoids.hasPfUI76 then
+            if playerGUID and durSpellName then
                 CleveRoids._allCasterAuraDirty = true
                 if not CleveRoids.AllCasterAuraTracking[playerGUID] then
                     CleveRoids.AllCasterAuraTracking[playerGUID] = {}