Add global WIDGETBOOK-INDEX.md and refactor use case method names for consistency across components

widgetbook/lib/button_group_m3e/button_group_m3e_usecases.dart

@@ -132,7 +132,7 @@ Clip _knobClipBehavior(BuildContext context, {Clip initial = Clip.none}) =>
     );
 
 @UseCase(name: 'default', type: ButtonGroupM3E)
-Widget buildButtonGroupM3EUseCase(BuildContext context) {
+Widget buildButtonGroupM3EDefaultUseCase(BuildContext context) {
   final ButtonGroupM3EType type = _knobType(context);
   final ButtonGroupM3EShape shape = _knobShape(context);
   final ButtonGroupM3ESize size = _knobSize(context);

widgetbook/lib/button_m3e/button_m3e_usecases.dart

@@ -118,7 +118,7 @@ Widget _buildDemo(
 }
 
 @UseCase(name: 'default', type: ButtonM3E)
-Widget buildButtonM3EUseCase(BuildContext context) {
+Widget buildButtonM3EDefaultUseCase(BuildContext context) {
   // Default uses filled style; other params adjustable with knobs
   return _buildDemo(context, style: ButtonM3EStyle.filled);
 }

widgetbook/lib/fab_m3e/fab_m3e_usecases.dart

@@ -78,7 +78,7 @@ Widget _buildFab(
 }
 
 @widgetbook.UseCase(name: 'default', type: FabM3E)
-Widget buildFabM3EUseCase(BuildContext context) {
+Widget buildFabM3EDefaultUseCase(BuildContext context) {
   return _buildFab(context, kind: FabM3EKind.primary);
 }
 

widgetbook/lib/icon_button_m3e/icon_button_m3e_usecases.dart

@@ -12,7 +12,7 @@ import 'package:widgetbook_annotation/widgetbook_annotation.dart';
 // - Complex objects get meaningful defaults with TODOs.
 
 @UseCase(name: 'default', type: IconButtonM3E)
-Widget buildIconButtonM3EUseCase(BuildContext context) {
+Widget buildIconButtonM3EDefaultUseCase(BuildContext context) {
   final bool isToggle = context.knobs.boolean(
     label: 'is toggle (provides selected state)',
     initialValue: true,

widgetbook/lib/loading_indicator_m3e/expressive_loading_indicator_usecases.dart

@@ -1,5 +1,3 @@
-
-
 import 'package:flutter/material.dart';
 import 'package:loading_indicator_m3e/loading_indicator_m3e.dart';
 import 'package:material_new_shapes/material_new_shapes.dart';
@@ -23,9 +21,17 @@ List<RoundedPolygon> _polygonSet(String id) {
     case 'cookie→oval':
       return [MaterialShapes.cookie9Sided, MaterialShapes.oval];
     case 'softBurst→pill→sunny':
-      return [MaterialShapes.softBurst, MaterialShapes.pill, MaterialShapes.sunny];
+      return [
+        MaterialShapes.softBurst,
+        MaterialShapes.pill,
+        MaterialShapes.sunny
+      ];
     case 'triangle→square→pentagon':
-      return [MaterialShapes.triangle, MaterialShapes.square, MaterialShapes.pentagon];
+      return [
+        MaterialShapes.triangle,
+        MaterialShapes.square,
+        MaterialShapes.pentagon
+      ];
     default:
       return [
         MaterialShapes.softBurst,
@@ -120,7 +126,9 @@ Widget buildExpressiveLoadingIndicatorColorAndSemanticsUseCase(
   );
 }
 
-@UseCase(name: 'edge: invalid polygons (debug assert)', type: ExpressiveLoadingIndicator)
+@UseCase(
+    name: 'edge: invalid polygons (debug assert)',
+    type: ExpressiveLoadingIndicator)
 Widget buildExpressiveLoadingIndicatorInvalidPolygonsUseCase(
     BuildContext context) {
   final enableInvalid = context.knobs.boolean(

widgetbook/lib/loading_indicator_m3e/loading_indicator_m3e_usecases.dart

@@ -53,7 +53,7 @@ List<RoundedPolygon> _polygonSet(String id) {
 }
 
 @UseCase(name: 'default', type: LoadingIndicatorM3E)
-Widget buildLoadingIndicatorM3EUseCase(BuildContext context) {
+Widget buildLoadingIndicatorM3EDefaultUseCase(BuildContext context) {
   // Keep defaults: tokens-based sizing and colors, subtle container.
   return const Center(
     child: LoadingIndicatorM3E(),

widgetbook/lib/navigation_rail_m3e/rail_badge_m3e_usecases.dart

@@ -1,12 +1,12 @@
 import 'package:flutter/material.dart';
+import 'package:navigation_rail_m3e/navigation_rail_m3e.dart';
 import 'package:widgetbook/widgetbook.dart';
 import 'package:widgetbook_annotation/widgetbook_annotation.dart' as widgetbook;
-import 'package:navigation_rail_m3e/navigation_rail_m3e.dart';
 
 // Note: RailBadgeM3E shows nothing when count is null; dot when 0; count otherwise.
 
 @widgetbook.UseCase(name: 'default', type: RailBadgeM3E)
-Widget buildRailBadgeM3EUseCase(BuildContext context) {
+Widget buildRailBadgeM3EDefaultUseCase(BuildContext context) {
   final count = context.knobs.intOrNull.slider(
     label: 'count',
     initialValue: 7,

widgetbook/lib/toolbar_m3e/toolbar_icon_button_m3e_usecases.dart

@@ -1,9 +1,7 @@
-
-
 import 'package:flutter/material.dart';
+import 'package:toolbar_m3e/toolbar_m3e.dart';
 import 'package:widgetbook/widgetbook.dart';
 import 'package:widgetbook_annotation/widgetbook_annotation.dart';
-import 'package:toolbar_m3e/toolbar_m3e.dart';
 
 @UseCase(name: 'default', type: ToolbarIconButtonM3E)
 Widget buildToolbarIconButtonM3EDefaultUseCase(BuildContext context) {
@@ -51,7 +49,8 @@ Widget buildToolbarIconButtonM3EDestructiveUseCase(BuildContext context) {
 }
 
 @UseCase(name: 'custom_color_and_size', type: ToolbarIconButtonM3E)
-Widget buildToolbarIconButtonM3ECustomStyleUseCase(BuildContext context) {
+Widget buildToolbarIconButtonM3ECustomColorAndSizeUseCase(
+    BuildContext context) {
   final color = context.knobs.color(label: 'color', initialValue: Colors.teal);
   final iconSize = context.knobs.double.slider(
     label: 'iconSize',