Decoupling Material and Cupertino from the core framework

[sfshaza2]

This is the first PR. The DartPad instances still use flutter/cupertino and flutter/material because DartPad can't handle the external packages yet.

[gemini-code-assist]

Code Review

This pull request updates package imports across numerous example files, replacing 'package:flutter/material.dart' and 'package:flutter/cupertino.dart' with 'package:material_ui/material.dart' and 'package:cupertino_ui/cupertino.dart' respectively. The review feedback correctly identifies a few files that inconsistently import 'package:cupertino_dart/cupertino.dart' instead of 'package:cupertino_ui/cupertino.dart', which could lead to compilation errors.

[gemini-code-assist]

Inconsistent package import. This file imports package:cupertino_dart/cupertino.dart, whereas other files in this pull request use package:cupertino_ui/cupertino.dart. This inconsistency will likely lead to compilation or import errors if cupertino_dart is not a valid or intended package name.

Suggested change

	import 'package:cupertino_dart/cupertino.dart';
	import 'package:cupertino_ui/cupertino.dart';

References

1. Report an issue only if the change introduces or worsens it, it's of medium severity or higher, and you can state its concrete consequence (e.g., incorrect API names or expected results). ^(link)

[gemini-code-assist]

Inconsistent package import. This file imports package:cupertino_dart/cupertino.dart, whereas other files in this pull request use package:cupertino_ui/cupertino.dart. This inconsistency will likely lead to compilation or import errors if cupertino_dart is not a valid or intended package name.

Suggested change

	import 'package:cupertino_dart/cupertino.dart';
	import 'package:cupertino_ui/cupertino.dart';

References

1. Report an issue only if the change introduces or worsens it, it's of medium severity or higher, and you can state its concrete consequence (e.g., incorrect API names or expected results). ^(link)

[gemini-code-assist]

Inconsistent package import. This file imports package:cupertino_dart/cupertino.dart, whereas other files in this pull request use package:cupertino_ui/cupertino.dart. This inconsistency will likely lead to compilation or import errors if cupertino_dart is not a valid or intended package name.

Suggested change

	import 'package:cupertino_dart/cupertino.dart';
	import 'package:cupertino_ui/cupertino.dart';

References

1. Report an issue only if the change introduces or worsens it, it's of medium severity or higher, and you can state its concrete consequence (e.g., incorrect API names or expected results). ^(link)

[gemini-code-assist]

Inconsistent package import. This file imports package:cupertino_dart/cupertino.dart, whereas other files in this pull request use package:cupertino_ui/cupertino.dart. This inconsistency will likely lead to compilation or import errors if cupertino_dart is not a valid or intended package name.

Suggested change

	import 'package:cupertino_dart/cupertino.dart';
	import 'package:cupertino_ui/cupertino.dart';

References

1. Report an issue only if the change introduces or worsens it, it's of medium severity or higher, and you can state its concrete consequence (e.g., incorrect API names or expected results). ^(link)