feat: add mitosis examples to generate storybook files next to showcase examples

[nmerget]

Proposed changes

The goal of this PR is to centralize all example definitions in Mitosis and automatically generate showcase outputs for all targets (React, Angular, Vue, Patternhub).

The PR provides

• a central example contract (*.examples.meta.ts that represents a typed metadata file for all examples, including identifiers, display names, grouping, and Storybook mappings)
• Mitosis-based showcase generation (created new *.showcase.lite.tsx components that consume the metadata, generate the corresponding React, Angular, and Vue showcase files and ensures a consistent structure across all frameworks)
• Showcase plugin architecture (plugin mechanism that provides the correct showcase component depending on the host context)
• Patternhub routing integration (updated routing so the button component now uses the new generated showcases and example pages)
• Output and build adjustments (correct file extensions and include generated meta files)

Types of changes

• Bugfix (non-breaking change that fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (improvements to existing components or architectural decisions)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Further comments

🔭🐙🐈 Test this branch here: https://design-system.deutschebahn.com/core-web/review/feat-examples-plugins

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[Copilot]

Pull request overview

This PR refactors the showcase architecture to use Mitosis-based examples that can generate both showcase and Storybook files. The key change is moving from JSON-based configuration files to .lite.tsx example files that are compiled to framework-specific code, establishing a single source of truth for component examples across showcases and Storybooks.

Key Changes

• Introduces Mitosis-based showcase architecture with .lite.tsx example files for the Button component
• Adds path alias configuration (@components) across all showcase projects for cleaner imports
• Removes JSON-based configuration (showcases/shared/button.json) in favor of TypeScript example files
• Creates reusable showcase wrapper components for consistent presentation across platforms

Reviewed changes

Copilot reviewed 95 out of 113 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/components/src/components/button/showcase/button.showcase.lite.tsx	New main showcase component for Button using Mitosis
packages/components/src/components/button/examples/*.lite.tsx	Individual example components for each Button variant/property
packages/components/src/components/button/examples/button.examples.meta.ts	Metadata defining all button examples with IDs and grouping
packages/components/src/shared/showcase/*.lite.tsx	Reusable wrapper components for showcase presentation
packages/components/configs/mitosis.showcase.config.cjs	New Mitosis configuration for compiling showcase files
showcases/shared/showcase-plugins.tsx	Plugin system for registering and retrieving showcase components
showcases/*/tsconfig.json	Path alias configuration for @components across all showcases
showcases/*/vite.config.ts	Vite alias configuration for @components
storybooks/react-storybook/src/stories/Variant.stories.tsx	Updated to use actual DBButton component
showcases/patternhub/scripts/generate-docs-mdx.js	Removed old code generation logic
output/*/tsconfig.json	Excludes showcase/example files from compilation
__snapshots__/button/showcase/**/*.yaml	Updated snapshots reflecting reordered examples

[mfranzke]

@michaelmkraus these seem to be middle instead of bottom aligned so some elements are now positioned centered instead of block-end. Is this expected and should have happened like this with this PR ?

[michaelmkraus]

No, that change is not intentional.
The centered vs. block-end alignment in the snapshot looks like an unintended side effect, likely coming from a shared wrapper that DBInput also uses. I’ll double-check the affected CSS.

[michaelmkraus]

Found the relevant CSS and reverted it.

[mfranzke]

@michaelmkraus these seem to be middle instead of top aligned so some elements are now positioned centered instead of block-start. Is this expected and should have happened like this with this PR ?

[michaelmkraus]

Found the relevant CSS and reverted it.

[mfranzke]

@michaelmkraus could you please add a description to this PR ? Why we did this change, on the expected outcome and a summary of the changes as well as what we need to do differently (in our processes) afterwards ?