feat(angular): add native angular container component sample to explorer

[josemontespg]

Summary

Demonstrates how developers can build native Angular container components in A2UI that host both native Angular and universal Web Component children within the same A2UI surface, and adds dynamic query parameter toggling (useUniversalComponent) for testing both rendering modes.

Key Changes

• Native Container Component (CustomGridComponent): Implemented a 4-cell responsive grid container in @a2ui/angular-explorer using @Component, CatalogComponentBase, and <a2ui-v09-component-host> to instantiate child slots dynamically.
• Example JSON (37_native-grid.json): Showcases CustomGrid hosting a mix of:
  • Native Angular components: CustomSlider with reactive two-way data binding mapped to independent paths (/sliderValue1 and /sliderValue2).
  • Universal Web Components: Card, Column, Text (with dynamic ${/path} string interpolation), and Button (with client action dispatching).
  • This example is placed in the core specification/v0_9/catalogs/basic/examples directory for cross-framework compatibility.
• Dynamic Universal Mode QueryParam:
  • Added useUniversalComponent URL query parameter support to both the A2UI Angular Explorer (renderers/angular/a2ui_explorer) and the Restaurant Finder Sample App (samples/client/angular/projects/restaurant).
  • Defaults to false (native Angular components) when absent, and enables W3C universal Web Components when ?useUniversalComponent=true.
• Test Suite & Verification:
  • Unit tests for CustomGridComponent.
  • Integration test suite (37_native-grid.spec.ts) verifying rendering, mixed child instantiation, and reactive data updates.
  • Manual Verification: Manually verified that both sample applications (A2UI Angular Explorer and Restaurant Finder) function as intended in both native and universal modes.

Pre-launch Checklist

• I read the [Contributors Guide].
• I read the [Style Guide].
• My code changes have tests.

Resolves #1270

[gemini-code-assist]

Code Review

This pull request introduces a new native Angular container component, CustomGridComponent, which implements a 2x2 grid layout capable of hosting both native and universal child components. It also adds corresponding unit tests, integration tests, and a demo example (37_native-grid.json). Additionally, the PR refactors the renderer configuration in DemoComponent to use provideA2Ui and updates DemoCatalog to extend BasicCatalogBase. The review feedback suggests a minor improvement in CustomGridComponent to use Angular 17's @if (value; as local) syntax to avoid redundant signal reads in the template.