fix(generator): support generic @MixWidget call methods

[leoafarias]

Summary

• allow @MixWidget to generate widgets from generic styler call<T>() methods
• preserve call type parameter bounds on the generated widget class
• forward generic type arguments when invoking the styler call method

Why

Remix needs generated Fortal widgets for generic radio and accordion APIs, e.g. FortalRadio<T> and FortalAccordion<T>. The published generator rejects generic call() methods today, which blocks reproducible code generation and pushes consumers toward hand-written widget drift.

Fixes #957.

Validation

• fvm dart pub get
• fvm dart test from packages/mix_generator passes, 277 tests

[Copilot]

Pull request overview

This PR updates mix_generator’s @MixWidget support to allow generating widgets from generic styler call<T>() methods, preserving type parameter bounds on the generated widget class and forwarding type arguments when invoking the styler call—unblocking generic Remix/Fortal-style APIs like FortalRadio<T>.

Changes:

• Extend MixWidgetGenerator to accept generic call<T>() methods when the return type is Widget-assignable (including T extends Widget), and validate type-parameter bound visibility.
• Add callTypeParams plumbing to the model/builder to emit generic widget classes and forward .call<T>() invocations.
• Add integration + unit test coverage for success cases and key rejection paths (non-widget bounds, hidden bound types, prefixed Flutter imports).

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/mix_generator/lib/src/mix_widget_generator.dart	Accepts/validates generic call<T>(), extracts type params/bounds, and enforces bound visibility + unprefixed Flutter base symbols.
packages/mix_generator/lib/src/core/models/mix_widget_model.dart	Adds WidgetCallTypeParam + model helpers for class generic declarations and call invocations.
packages/mix_generator/lib/src/core/builders/mix_widget_builder.dart	Emits generic widget class declarations and forwards type args on .call<...>().
packages/mix_generator/test/integration/generator_smoke_test.dart	Adds end-to-end smoke tests asserting generated output for generic widgets and forwarded type args.
packages/mix_generator/test/integration/generator_validation_test.dart	Adds validation tests for invalid generic-return shapes and bound visibility/import constraints.
packages/mix_generator/test/core/builders/mix_widget_builder_test.dart	Adds unit tests for generic class emission, bound preservation, and type-arg forwarding in the builder.
packages/mix_generator/pubspec.yaml	Bumps package version to 2.1.2.
packages/mix_generator/CHANGELOG.md	Documents the new fix in 2.1.2.