perf(l10n): add zero-arg fast path to translate

_l10n:translate now short-circuits the common no-argument case
(select('#', ...) == 0), returning the translation directly and skipping
the {...} allocation, the tostring loop, and safeFormat. Behavior matches
the slow path: a successful no-arg lookup already returned the raw value,
and missing/invalid entries fall back to the key. Cherry-picked from
phase2-lua50-sweep.

Localization/l10n.lua

@@ -191,6 +191,33 @@ function _l10n:translate(key, ...)
         return ""
     end
     key = tostring(key)
+    local argCount = select("#", ...)
+    if argCount == 0 then
+        local translationEntry = l10n.translations[key]
+        if not translationEntry then
+            if (Questie.db.profile.debugEnabled) then Questie:Debug(Questie.DEBUG_ELEVATED, "ERROR: Translations for '" .. tostring(key) .. "' are missing completely!") end
+            return key
+        end
+
+        local translationValue = translationEntry[locale]
+        if (not translationValue) then
+            if (Questie.db.profile.debugEnabled) then Questie:Debug(Questie.DEBUG_ELEVATED, "ERROR: Translations for '" .. tostring(key) .. "' are missing the entry for language" , locale, "!") end
+            return key
+        end
+
+        if translationValue == true then
+            -- Fallback to enUS which is the key
+            return key
+        end
+
+        if type(translationValue) ~= "string" then
+            if (Questie.db.profile.debugEnabled) then Questie:Debug(Questie.DEBUG_ELEVATED, "ERROR: Translation for '" .. tostring(key) .. "' is not a string!") end
+            return key
+        end
+
+        return translationValue
+    end
+
     local args = {...}
 
     for i, v in ipairs(args) do