re-add tightening and use it when messing with scopes

e.g. "coe [_ ⇒ A] @p @q s" should immediately reduce to "s",
but if the "_ ⇒ A" happened to use an SY it didn't.

this will still happen if a wrong SY sneaks in but the alternative is
re-traversing the term over and over every time whnf runs

lib/Quox/Parser/FromParser.idr

@@ -164,9 +164,8 @@ mutual
         <*> fromPDimWith ds q
         <*> fromPTermWith ds ns val
 
-    -- [todo] direct translation for homo comp?
     Comp (i, ty) p q val r (j0, val0) (j1, val1) =>
-      map E $ CompH
+      map E $ CompH'
         <$> fromPTermDScope ds ns [< i] ty
         <*> fromPDimWith ds p
         <*> fromPDimWith ds q
@@ -201,7 +200,7 @@ mutual
     if all isNothing xs then
       SN <$> fromPTermWith ds ns t
     else
-      SY (fromSnocVect $ map (maybe Unused UN) xs)
+      ST (fromSnocVect $ map (maybe Unused UN) xs)
         <$> fromPTermWith ds (ns ++ xs) t
 
   private
@@ -213,7 +212,7 @@ mutual
     if all isNothing xs then
       SN <$> fromPTermWith ds ns t
     else
-      SY (fromSnocVect $ map (maybe Unused UN) xs)
+      DST (fromSnocVect $ map (maybe Unused UN) xs)
         <$> fromPTermWith (ds ++ xs) ns t