Add AI-powered StepperView generator with on-device Foundation Models

[badrinathvm]

Description

• Add StepperViewAIGeneratorView with prompt input, live preview, and code generation tabs
• Add StepperAIBuilder to map AI-generated configs to StepperView API calls
• Add @generable model structs for Foundation Models structured output (iOS 26+)
• Externalize AI config to YAML (ai_config.yaml) with Yams dependency
• Support hex colors and expanded named color palette for AI generation
• Enforce uniform indicators, colors, and pit stop rules via post-processing
• Update .gitignore to exclude Pods/ and Package.resolved
• Remove outdated @available annotations across codebase

Type of change

• Bug fix
• New feature
• Breaking change
• This change requires a documentation update

How Has This Been Tested

Please let us know if you have tested your PR and if we need to reproduce the issues. Also, please let us know if we need any relevant information for running the tests.

• Unit Testing
• UI Testing

Test Configuration

• Xcode version:
• Device/Simulator
• iOS version
• MacOSX version

Checklist:

For checklist items not applicable, mention NA in front of it with some comment if applicable.

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• Add comments to code particularly in hard-to-understand areas
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes before pushing the pull request