Source: docs/WORKBENCH-VNEXT.md and docs/TODO.md
Persist baseplate design inputs and derived layout metadata so a saved Workbench item can be reopened with the same preview-relevant state.
Acceptance criteria:
- Save the generator input model for a baseplate design.
- Persist derived dimensions, tile count, split plan, validation state, and warnings.
- Restore saved designs on item load.
- Add optimistic concurrency for mutable design records.
Source: docs/WORKBENCH-VNEXT.md and docs/TODO.md
Persist baseplate design inputs and derived layout metadata so a saved Workbench item can be reopened with the same preview-relevant state.
Acceptance criteria: