channels/base.py: GatewayInvocation dataclass + Channel ABC
(parse_invocation/render_result), mirroring Rein one layer up -- a
channel turns an external invocation into what run_task_through_rein
needs, and turns its result back into whatever the invocation medium
expects.
channels/cli_channel.py: CLIChannel, a pure refactor of what cli.py did
inline -- argparse Namespace -> GatewayInvocation, result dict ->
json.dumps(..., indent=2). cli.py's run handler is now a thin
construct-parse-invoke-render wrapper.
docs/channel-contract.md documents the pattern and sketches (without
building) a second channel.
Found and fixed a real bug while live-testing this refactor:
ReinAharness's default cli_bin was still "agent-harness", stale from
before HARNESS-WP-0002-T02's rename.
4 new tests (27/27 passing), plus a real live run through
python3 -m glas_harness.cli against rein-aharness/real Claude Code
confirming identical output shape and a real commit.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
