Remove consP HACK rule and removeIndexTail from RawPtr aggregate

The consP rule that merged ConstantIndex with PointerOffset was
a workaround for a deeper issue: removeIndexTail in
#mkAggregate(aggregateKindRawPtr) strips the element-extraction
CI(0) when constructing fat pointers from thin pointers, but
#typeProjection later adds per-element navigation projections
(Field for MaybeUninit→ManuallyDrop→T) that assume the element
has already been extracted.

Removing removeIndexTail preserves the CI(0) through the fat
pointer construction, allowing the subsequent #typeProjection
projections to correctly navigate into individual array elements.

The consP HACK rule is also removed as it is no longer needed
and was conceptually unsound (merging projections from different
semantic levels).

The iterator-simple test now reaches a different stuck state:
PointerOffset(1,0) applied to a scalar Integer after successful
element navigation, which is closer to the real remaining issue
(projection ordering between CI and PointerOffset).

See #1011.

Author: Stevengre

kmir/src/kmir/kdist/mir-semantics/rt/data.md

@@ -384,9 +384,6 @@ These helpers mark down, as we traverse the projection, what `Place` we are curr
   rule consP(projectionElemWrapStruct, projectionElemField(fieldIdx(0), _) PS:ProjectionElems) => PS [priority(40)]
   // this rule is not valid if the original pointee has more than one field
   // rule consP(projectionElemField(fieldIdx(0), _), projectionElemWrapStruct PS:ProjectionElems) => PS [priority(40)]
-  // HACK: special rule which munges together constant-indexing and offset projections 
-  rule consP( projectionElemConstantIndex(I, 0, false), PointerOffset(OFF, _SIZE) PS) => projectionElemConstantIndex(I +Int OFF, 0, false) PS [priority(40)]
-    // requires I +Int OFF < _SIZE // _SIZE is metadataSize, needs a < operation for this to work
   rule consP(projectionElemToZST, projectionElemFromZST PS:ProjectionElems) => PS [priority(40)]
   rule consP(projectionElemFromZST, projectionElemToZST PS:ProjectionElems) => PS [priority(40)]
 
@@ -1113,7 +1110,7 @@ and an array of the indeicated size gets reconstructed if the provided metadata
   rule <k> ListItem(PtrLocal(OFFSET, place(LOCAL, PROJS), _, metadata(_SIZE, PTR_OFFSET, ORIGIN_SIZE))) 
            ListItem(Integer(LENGTH, 64, false))
            ~> #mkAggregate(aggregateKindRawPtr(_TY, MUT))
-        => PtrLocal(OFFSET, place(LOCAL, removeIndexTail(PROJS)), MUT, metadata(dynamicSize(LENGTH), PTR_OFFSET, ORIGIN_SIZE))
+        => PtrLocal(OFFSET, place(LOCAL, PROJS), MUT, metadata(dynamicSize(LENGTH), PTR_OFFSET, ORIGIN_SIZE))
         ...
        </k>
     // requires LENGTH +Int PTR_OFFSET <=Int ORIGIN_SIZE // refuse to create an invalid fat pointer

kmir/src/tests/integration/data/prove-rs/show/iterator-simple-fail.main.expected

@@ -3,9 +3,9 @@
 │   #execTerminator ( terminator ( ... kind: terminatorKindCall ( ... func: operandC
 │   span: 0
 │
-│  (1066 steps)
+│  (1069 steps)
 └─ 3 (stuck, leaf)
-    #traverseProjection ( toStack ( 3 , local ( 3 ) ) , Range ( ListItem ( Union ( f
+    #traverseProjection ( toStack ( 3 , local ( 3 ) ) , Integer ( 1 , 32 , true ) ,
     span: 106