fix(pointer-casts): support array-to-wrapper projections

[Stevengre]

Summary

• relax transparent-wrapper pointee projection so array-to-wrapper pointer casts can advance
• cover wrapper, nested-wrapper, and singleton-wrapped-array pointer cast regressions with one shared semantic fix

Test plan

• cd kmir && uv run pytest src/tests/integration/test_integration.py -k "ptr-cast-array-to-wrapper-fail or ptr-cast-array-to-nested-wrapper-fail or ptr-cast-array-to-singleton-wrapped-array-fail or ptr-through-wrapper-fail or raw-ptr-cast-fail or ref-ptr-cast-elem-fail or ref-ptr-cast-elem-offset-fail or pointer-cast-length-test-fail" -q

[Stevengre]

Closing: the array-to-wrapper pointer cast regressions this PR targeted are addressed by #1003 (stable address allocation model). The semantic rule changes here had no observable effect on the claimed test cases — all 8 proofs stuck at the same thunk(#cast(...)) point with identical proof trees before and after the changes.