Implemented streaming transformations:

- Added `tostream`, `fromstream`, and `truncate_stream`.
- Preserved depth-first ordering and stream record shapes.
- Added focused tests; 10 streaming tests pass.
- Conformance selector matched zero staged cases because `jq.test` contains no streaming names.

AC_BROKEN: io-003-conformance

RESULT: SUCCESS

FILES CHANGED:
- jq_interpreter/evaluator.py
- jq_interpreter/parser.py
- tests/test_stream_evaluator.py

SUMMARY:
Streaming filters implemented and locally verified, including round-trip reconstruction and truncation.

BLOCKERS:
- Declared conformance criterion is broken by the staged corpus containing zero matching cases.