RESULT: SUCCESS

FILES CHANGED:
- jq_interpreter/cli.py
- jq_interpreter/evaluator.py
- jq_interpreter/interpreter.py
- jq_interpreter/parser.py
- tests/test_json_io.py

SUMMARY:
Implemented `input`, `inputs`, `input_filename`, and `input_line_number` with shared stdin stream state and metadata tracking.

Verification:
- Both IO-001 scoped gates passed.
- Full test suite: 173 passed.

BLOCKERS:
- None