fix(manhattan-recovery): update TyArrow arity to 4-args in parser + julia backend

The Manhattan Recovery commit bundled the pre-existing grammar refactor
that added a quantity field to TyArrow (3-arg -> 4-arg). Two call sites
in parser.mly (type_expr_arrow productions) and julia_codegen.ml
(type_expr_to_julia_string) were at line locations where the auto-merge
with origin/main took upstream's 3-arg version without conflict markers.

Post-cherry-pick build fix — adds the missing quantity argument (None)
in all three call sites. No semantic change.

Author: hyperpolymath

lib/julia_codegen.ml

@@ -57,7 +57,7 @@ let rec type_expr_to_julia_string (te : type_expr) : string =
   | TyCon name when name.name = "String" -> "String"
   | TyCon name when name.name = "Unit" -> "Nothing"
   | TyCon name -> name.name  (* Custom type names pass through *)
-  | TyArrow (_, ret, _) ->
+  | TyArrow (_, _, ret, _) ->
       (* Function types: for now, just use ret type annotation *)
       type_expr_to_julia_string ret
   | TyTuple tys ->

lib/parser.mly

@@ -249,9 +249,9 @@ type_expr:
 
 type_expr_arrow:
   | arg = type_expr_primary ARROW ret = type_expr_arrow
-    { TyArrow (arg, ret, None) }
+    { TyArrow (arg, None, ret, None) }
   | arg = type_expr_primary MINUS LBRACE eff = effect_expr RBRACE ARROW ret = type_expr_arrow
-    { TyArrow (arg, ret, Some eff) }
+    { TyArrow (arg, None, ret, Some eff) }
   | ty = type_expr_primary { ty }
 
 type_expr_primary: