Implemented VALUE-003 slices and collection iteration, including fractional bounds, null handling, ordering, multiplicity, and optional iteration.

RESULT: SUCCESS

FILES CHANGED:
- jq_interpreter/evaluator.py
- tests/test_value_003_slices_iteration.py

SUMMARY:
73 tests passed. Scoped conformance: 144 passed, 0 failed, 0 errored, 4 skipped.

BLOCKERS:
- None