linq_fold: PR F3 R1 — drop redundant clone_type(elemType) (Copilot #1)

Copilot flagged emit_decs_early_exit's `retType = clone_type(elemType)`
as a double-clone since `elemType` is already `clone_type(chainInfo.finalType)`.
Same pattern appeared in 3 emit_decs_walk_lane arms (last / single /
single_or_default).

Both `elemType` and `retType` get qmacro-spliced (apply_template clones
its inputs internally), so the explicit clone is wasted work. Sharing the
elemType pointer between the var-decl splice and the invoke retType splice
is safe — each splice clones independently at emit time.

AST byte-identical to pre-fix dump on the same 6-chain baseline.
tests/linq green (1689/1689).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: borisbat

daslib/linq_fold.das

@@ -5423,7 +5423,7 @@ def private emit_decs_early_exit(bridge : DecsBridgeShape?;
     var dispatch : DecsDispatch = DecsDispatch(Find = null)
     var retType : TypeDeclPtr
     if (opName == "first" || opName == "first_or_default") {
-        retType = clone_type(elemType)
+        retType = elemType
         preludeStmts |> push_from <| qmacro_block_to_array() {
             var $i(foundName) = false
             var $i(resultName) : $t(elemType)
@@ -5680,7 +5680,7 @@ def private emit_decs_walk_lane(bridge : DecsBridgeShape?;
     var retType : TypeDeclPtr
     var earlyExitFind = false
     if (opName == "last" || opName == "last_or_default") {
-        retType = clone_type(elemType)
+        retType = elemType
         let foundName = qn("decs_found", at)
         let bindName = qn("decs_lst", at)
         preludeStmts |> push_from <| qmacro_block_to_array() {
@@ -5708,7 +5708,7 @@ def private emit_decs_walk_lane(bridge : DecsBridgeShape?;
             }
         }
     } elif (opName == "single") {
-        retType = clone_type(elemType)
+        retType = elemType
         let foundName = qn("decs_found", at)
         let bindName = qn("decs_sng", at)
         preludeStmts |> push_from <| qmacro_block_to_array() {
@@ -5726,7 +5726,7 @@ def private emit_decs_walk_lane(bridge : DecsBridgeShape?;
             return <- $i(bindName)
         }
     } elif (opName == "single_or_default") {
-        retType = clone_type(elemType)
+        retType = elemType
         let foundName = qn("decs_found", at)
         let stopName = qn("decs_stop", at)
         let bindName = qn("decs_sng", at)