Add Growl pet auto-teach feature and smooth zButton expand animation

- New Pet Auto-Teach: on tame, offer to teach Growl at the best rank via the
  Beast Training window (Craft API DoCraft), with a General options checkbox
  and /mth growl on|off|status toggle (on by default).
- De-stagger zButton flyout bars and zBar so buttons fade in together.
- Update CHANGELOG.

api/core-scan-stablemaster.lua

@@ -3104,6 +3104,9 @@ function MTH_PETS_RefreshCurrentPet()
 				at = now,
 				context = eventContext,
 			})
+			if eventType == "pet-tamed" and type(MTH_Growl_OfferForTamedPet) == "function" then
+				MTH_Growl_OfferForTamedPet(snapshot.name, snapshot.level)
+			end
 		end
 
 	end
@@ -3733,6 +3736,9 @@ local function MTH_PETS_HandleUnitPetTransition(source)
 					context = MTH_PETS_CaptureContext(),
 				})
 			end
+			if eventType == "pet-tamed" and type(MTH_Growl_OfferForTamedPet) == "function" then
+				MTH_Growl_OfferForTamedPet(snapshot.name, snapshot.level)
+			end
 		end
 		if not hadPet and hasPendingTame then
 			MTH_PETS_LogTame("Acquire completed; clearing pending tame attempt")