Reusable step library entry. Carries the same shape fields as
fusion.plating.process.node so a drag-drop snapshot is a 1:1 copy.
DEFAULT_INPUTS_BY_KIND drives seeding for the 15 kinds we identified
on Steelhead's job traveller (cleaning, etch, plate, bake, etc.).
The seeding helper (_seed_default_inputs) is idempotent — won't
duplicate inputs on repeated calls.
Note: imports for the 2 child models (input + transition_input) are
added in models/__init__.py here; the actual files land in the next
two commits. Module won't load cleanly on entech until both ship.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
bef812616b
