fix: align v0.9 slider schema with spec

[kiwigitops]

Closes #1384.

Summary

• remove the non-spec step property from the v0.9 WebCore SliderApi schema
• stop the Angular v0.9 slider from reading that non-spec prop
• add a v0.9 schema regression so Slider.step is rejected instead of diverging from the frozen JSON catalog

Verification

• npm test -- --watch=false from renderers/web_core
• npx ng build lib from renderers/angular

[gemini-code-assist]

Code Review

This pull request removes the step property from the SliderApi schema and the corresponding Angular SliderComponent. A regression test was added to verify that the schema now rejects the step property. Feedback suggests improving the robustness of this test by ensuring it specifically fails due to the unrecognized step key rather than other potential validation errors, and provided a code suggestion to implement this check.

[gemini-code-assist]

The regression test for SliderApi should be more robust. Currently, assert.throws will pass if the schema parsing fails for any reason (e.g., an invalid value format or missing required fields). To ensure it specifically catches the rejection of the step property, it is better to first validate a correct object and then verify that adding step causes a specific error. Additionally, using a literal number for value is more consistent with other tests in this file.

    it('should reject non-spec step property', () => {
      const validSlider = {
        max: 100,
        value: 50,
      };
      // Verify it parses correctly without the 'step' property
      SliderApi.schema.parse(validSlider);

      const invalidSlider = {
        ...validSlider,
        step: 5,
      };

      assert.throws(
        () => SliderApi.schema.parse(invalidSlider),
        /unrecognized_keys.*step/i
      );
    });

[kiwigitops]

Tightened the regression in 192683b so it first verifies the slider parses without step, then checks that adding step is rejected as the unrecognized key. npm test -- --watch=false still passes in renderers/web_core.