refactor(atomic): migrate atomic-tab-button from Stencil to Lit

[Copilot]

No e2e, stories or mdx needed as this is an internal component.

✅ Checklist

• 🧪 The component is unit tested
• 🧪 The component includes E2E tests
• 🗑️ Old Cypress tests exclusive to the component are removed
• 📖 The component is documented in storybook with an .mdx file
• ♿ 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.
• 🎨 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
• 🏷️ The component declares the component type in the HTMLElementTagNameMap

https://coveord.atlassian.net/browse/KIT-5024
close #6377

[Copilot]

Pull request overview

This PR migrates the atomic-tab-button component from Stencil to Lit as part of the broader Stencil-to-Lit migration effort. The component is marked as internal, so e2e tests, Storybook stories, and MDX documentation are not required per the PR description.

Key Changes:

• Migrated atomic-tab-button from Stencil to Lit with Tailwind CSS styling
• Updated unit tests to use Vitest instead of the previous testing framework
• Updated atomic-tab-manager to use the new Lit component and corrected role from "list" to "tablist"

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
packages/atomic/src/components/common/atomic-tab-button/atomic-tab-button.ts	New Lit implementation of tab button component with shadow DOM and Tailwind styles
packages/atomic/src/components/common/atomic-tab-button/atomic-tab-button.spec.ts	Migrated unit tests to Vitest with updated test structure
packages/atomic/src/components/search/atomic-tab-manager/atomic-tab-manager.ts	Updated to import and use new Lit tab button, changed container role from "list" to "tablist"
packages/atomic/src/components/search/atomic-tab-manager/e2e/page-object.ts	Updated locator from label-based to role-based for better semantic querying
packages/atomic/src/components/common/index.ts	Exported new AtomicTabButton component
packages/atomic/src/components/common/lazy-index.ts	Added lazy loading entry for atomic-tab-button
packages/atomic/src/utils/custom-element-tags.ts	Registered 'atomic-tab-button' custom element tag
packages/atomic/src/components/common/tabs/stencil-tab-button.tsx	Removed old Stencil implementation
packages/atomic/src/components/common/tabs/tab-button.ts	Removed old functional component implementation
packages/atomic/src/components/common/tabs/tab-button.pcss	Removed old PostCSS styles
packages/atomic/src/components.d.ts	Removed Stencil-generated type definitions for atomic-tab-button

Comments suppressed due to low confidence (2)

packages/atomic/src/components/common/atomic-tab-button/atomic-tab-button.spec.ts:51

• The test is checking for role="listitem" but the implementation uses role="tab". This test should be updated to verify role="tab" instead. The container query querySelector('[role="listitem"]') on line 25 will return null, causing test failures.
  packages/atomic/src/components/common/atomic-tab-button/atomic-tab-button.spec.ts:25
• The getContainer() function queries for '[role="listitem"]' but the implementation renders role="tab". This selector should be '[role="tab"]' to match the actual implementation.

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