refactor(atomic): migrate FacetSegmentedValue functional component to Lit

[Copilot]

Description

Migrates the FacetSegmentedValue functional component from Stencil to Lit. This is a rendering function used by atomic-segmented-facet, not a standalone web component.

Changes

• Lit Implementation (facet-segmented-value.ts)

  • Uses FunctionalComponent<FacetValuePropsBase> type signature
  • Replaces Stencil's Button with Lit's renderButton
  • Applies keyed directive for list item stability
  • Maintains existing functionality: segmented button with label and compact count formatting

• Backward Compatibility

  • Renamed original to stencil-facet-segmented-value.tsx
  • Updated atomic-segmented-facet.tsx import to use prefixed version
  • No breaking changes to existing Stencil components

• Unit Tests (facet-segmented-value.spec.ts)

  • 21 test cases: rendering, props, ARIA attributes, styling states
  • Uses renderFunctionFixture pattern consistent with other functional component tests
  • Predictable assertions based on stable English locale from createTestI18n()
  • Exact number format expectations (e.g., 1234 → (1.2K), 987654321 → (988M))

✅ Checklist

• 🧪 The component is unit tested
• 🧪 The component includes E2E tests (N/A - functional component)
• 🗑️ Old Cypress tests exclusive to the component are removed (N/A - no existing tests)
• 📖 The component is documented in storybook with an .mdx file (N/A - functional component)
• ♿ The component complies with the Web Content Accessibility Guidelines
• 🌐 All strings intended for humans or assistive technology must be localized with i18n
• 📦 The Lit component is exported in the appropriate index.ts and lazy-index.ts files (N/A - internal functional component)
• 🎨 CSS parts are documented still accessible
• 🦥 Slotted Content, public methods and properties are documented
• 🔄 The component outputs the same Angular output as before with Stencil (N/A - functional component)
• 🏷️ The component declares the component type in the HTMLElementTagNameMap (N/A - functional component)

https://coveord.atlassian.net/browse/KIT-4956

Original prompt

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This section details on the original issue you should resolve

<issue_title>Migrate FacetSegmentedValue</issue_title>
<issue_description>

Jira Issue: KIT-4956

Type: User Story
Status: New
Priority: Medium
Components: Atomic

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Comments on the Issue (you are @copilot in this section)

Custom agent used: stencil-to-lit-migration-agent
Specialized agent for migrating Atomic Stencil code to Lit (components, functional components, and utils)

• Fixes Migrate FacetSegmentedValue #6402

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✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[louis-bompart]

@copilot some work on the ut, make them more "stable" & reliable.
Do consider also that this is a functionnal component. We Unit Test those: if you need more mocks, go ahead.

[Copilot]

@copilot some work on the ut, make them more "stable" & reliable.
Do consider also that this is a functionnal component. We Unit Test those: if you need more mocks, go ahead.

Done! I've improved the tests to be more stable and reliable:

1. Predictable assertions: Changed vague checks to exact number format expectations (e.g., (1.2K), (1.2M), (988M)) based on the stable English locale
2. Added clarity: Added a comment explaining that createTestI18n() provides a stable locale for consistent formatting
3. Removed redundancy: Removed a duplicate test that was just checking if a list item exists

All tests now have specific, predictable expectations. Commit: 7d87568

[Copilot]

Pull request overview

This PR migrates the FacetSegmentedValue functional component from Stencil to Lit. The component renders segmented facet values with a button, label, and compact count formatting used by atomic-segmented-facet.

Key changes:

• New Lit implementation using FunctionalComponent<FacetValuePropsBase> type signature
• Applies keyed directive for list stability and uses renderButton instead of Stencil's Button
• Comprehensive test suite with 21 test cases covering rendering, props, ARIA attributes, and styling

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 3 comments.

File	Description
stencil-facet-segmented-value.tsx	Renamed original Stencil implementation with deprecation notice for backward compatibility
facet-segmented-value.ts	New Lit functional component replacing Stencil version with equivalent functionality
facet-segmented-value.spec.ts	New unit tests for Lit component covering rendering, accessibility, and interaction scenarios
atomic-segmented-facet.tsx	Updated import to use prefixed Stencil version maintaining backward compatibility

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[fbeaudoincoveo]

GG!