Refactor: split ImportWizard into pure ImportPipeline and UI wrapper

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>

src/command/dispatch.rs

@@ -196,20 +196,17 @@ fn import_json_headless(
 
     let proposals = analyze_records(&records);
 
-    // Auto-accept all and build
-    let wizard = crate::import::wizard::ImportWizard {
-        state: crate::import::wizard::WizardState::NameModel,
+    // Auto-accept all and build via ImportPipeline
+    let pipeline = crate::import::wizard::ImportPipeline {
         raw: value,
         array_paths: vec![],
         selected_path: array_path.unwrap_or("").to_string(),
         records,
         proposals: proposals.into_iter().map(|mut p| { p.accepted = p.kind != FieldKind::Label; p }).collect(),
         model_name: model_name.unwrap_or("Imported Model").to_string(),
-        cursor: 0,
-        message: None,
     };
 
-    match wizard.build_model() {
+    match pipeline.build_model() {
         Ok(new_model) => {
             *model = new_model;
             CommandResult::ok_msg("JSON imported successfully")