[BUG] Fix `ztensor_slice_dim4` Invalid-Layout Error Message (Report Pre-Transformed Layout)

[k8ika0s]

Proposed PR branch: qe/issue-05-slice-dim4-error-message

Category: Bug (diagnostic correctness)

Problem

• ztensor_slice_dim4 invalid-layout errors should reference the
  pre-transformed layout. Incorrect wording makes integration debugging
  significantly harder.

Justification / why this is needed

• Error messages are part of the API contract for integrators; incorrect
  layout references can waste significant debugging time and lead to incorrect
  “fixes” in upstream frameworks.
• Baseline+regtests showed this expectation failing; enhanced passes.

Proposed change

• Fix the invalid-layout error message to report pre-transformed layout.
• Add a regression test that asserts error message content.

Acceptance criteria

• Error message references the correct layout domain (pre vs transformed).
• Regression test locks behavior.

Test plan

• make test (expects tests/testDriver_slice_dim4_error_message.c to pass).

References

• Baseline report: artifacts/FINAL_BASELINE_ENHANCEMENT_REPORT.md shows this
  was failing on baseline+regtests and passing in enhanced.
• Key files: zdnn/tensor_desc.c, tests/testDriver_slice_dim4_error_message.c.