Remove temporary bridge rules from #traverseProjection

The two bridge rules added in bed3503 (Union-unwrap for Field,
and bare-value-to-Range for PointerOffset) treated a symptom
rather than the root cause. The real issue is in how
removeIndexTail and #typeProjection interact during pointer
construction and PtrToPtr casts for slice types.

Removing these rules exposes the underlying stuck state so the
proper fix can be validated against it.

See #1011 for the planned structural fix.

Author: Stevengre

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

@@ -509,16 +509,6 @@ The following rule resolves this situation by using the head element.
         => #traverseProjection(DEST, VALUE, projectionElemField(IDX, TY) PROJS, CTXTS) ... </k> // TODO mark context?
     [preserves-definedness, priority(100)]
 
-  // Temporary bridge rule: after PointerOffset lifts a single value to Range(ListItem(...)),
-  // unwrap a Union head element so the existing Union + Field rules below can keep running.
-  rule <k> #traverseProjection(
-             DEST,
-             Range(ListItem(Union(_, _) #as VALUE) _REST:List),
-             projectionElemField(IDX, TY) PROJS,
-             CTXTS
-           )
-        => #traverseProjection(DEST, VALUE, projectionElemField(IDX, TY) PROJS, CTXTS) ... </k> // TODO mark context?
-    [preserves-definedness, priority(100)]
 ```
 
 #### Unions
@@ -660,24 +650,6 @@ Similar to `ConstantIndex`, the slice _end_ index may count from the _end_  or t
      andBool START <=Int size(ELEMENTS) -Int END
     [preserves-definedness] // Indexes checked to be in range for ELEMENTS
 
-  // Temporary bridge rule: PointerOffset is implemented below in terms of Range slicing, so
-  // lift a single non-Range value to Range(ListItem(...)) to reuse that shared path.
-  rule <k> #traverseProjection(
-             DEST,
-             VAL,
-             PointerOffset(OFFSET, ORIGIN_LENGTH) PROJS,
-             CTXTS
-           )
-        => #traverseProjection(
-             DEST,
-             Range(ListItem(VAL)),
-             PointerOffset(OFFSET, ORIGIN_LENGTH) PROJS,
-             CTXTS
-           )
-        ...
-        </k>
-    requires notBool isRange(VAL)
-    [preserves-definedness, priority(100)]
 
   rule <k> #traverseProjection(
              DEST,