Disk-backed image bus (input/gate_bus/<id>/): gates auto-publish image+mask
to a named send_id on pass; when image input is empty they load from get_id
(dropdown) — wireless, cycle-free "restart from the gate point" across runs.
Making image optional implements ignore-on-normal-path. TDD plan with a pure
stdlib imagebus + tensor savers; comfy imports stay lazy.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
