Implemented recursive generator primitives.

- Added correct `while`, `until`, `repeat`, `recurse`, and recursive descent behavior.
- Added focused FLOW-006 tests.
- Tests: 106 passed.
- Scoped conformance: 2 passed, 0 failed, 0 errored.

RESULT: SUCCESS

FILES CHANGED:
- jq_interpreter/evaluator.py
- tests/test_flow_006_recursive_generators.py

SUMMARY:
Recursive generators now preserve jq stream ordering, branching, termination, and partial output behavior.

BLOCKERS:
- None