Removes dead use statements across dispatch, formula, import, model, and
UI modules. Prefixes intentionally unused variables with _ in app.rs,
analyzer.rs, and grid.rs.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
ImportPipeline holds all data and logic (raw JSON, records, proposals,
model_name, build_model). ImportWizard wraps it with UI-only state
(step, cursor, message). Rename WizardState → WizardStep throughout.
Headless import in dispatch.rs now constructs ImportPipeline directly.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>