## Summary
This PR continues the TFLite frontend work tracked in #18971 for
`STRIDED_SLICE` and `SPLIT_V`.
Since the dynamic `FILL` / `SPLIT_V` partial-implementation work has
already been handled separately in #19433, this PR focuses on the
remaining pieces in this branch:
- fixing negative-stride `STRIDED_SLICE` conversion in the TFLite
frontend
- adding regression coverage for `STRIDED_SLICE` and static `SPLIT_V`
Relates to #18971.
## Changes
1. **`STRIDED_SLICE` negative-stride fix**
- Update the TFLite frontend `convert_strided_slice` handling of
`end_mask` when `stride < 0`.
- Use an exclusive lower bound compatible with Relax slicing semantics
so reverse slices like `x[::-1]` include index `0` correctly.
2. **TFLite frontend test coverage**
- Add `test_strided_slice_stride` to cover non-unit stride handling.
- Add `test_strided_slice_negative_stride` to cover reverse slicing with
negative strides.
- Add `test_split_v_static` to cover static `SPLIT_V` conversion.
3. **Scope clarification**
- Keep this PR focused on the remaining `STRIDED_SLICE` / `SPLIT_V` work
from #18971.
- Exclude the dynamic `FILL` / `SPLIT_V` changes that are already
addressed in #19433.
## Testing
```bash
python -m pytest -n 1
tests/python/relax/test_frontend_tflite.py::test_split_v_static -q
python -m pytest -n 1
tests/python/relax/test_frontend_tflite.py::test_strided_slice_stride -q
python -m pytest -n 1
tests/python/relax/test_frontend_tflite.py::test_strided_slice_negative_stride
-q
```
## Result
- The added STRIDED_SLICE and SPLIT_V tests passed locally.
- The negative-stride STRIDED_SLICE path now matches Relax slicing semantics.
HoYi
90c678abc9