feat(chat): Implemented reactive adoptRootStyles with dedicated controller

[rkaraivanov]

Description

Added a new AdoptedStylesController that enables chat components to dynamically adopt document-level styles into Shadow DOM with proper lifecycle management.

Changes:

• Created src/components/common/controllers/adopt-styles.ts

  • Reactive controller for managing document style adoption
  • Implements WeakMap-based caching per document for performance
  • Provides cache invalidation for theme changes
  • Handles cross-origin stylesheet restrictions gracefully
  • Automatic cleanup on component disconnection

• Updated chat-input.ts and chat-message.ts

  • Migrated from inline controller to shared adopt-styles controller
  • Added reactive _shouldAdoptRootStyles state property
  • Implemented proper update() lifecycle to respond to option changes
  • Added cache invalidation on theme changes via _adoptPageStyles()

• Enhanced chat.spec.ts

  • Added ResizeObserver loop error suppression for test stability
  • Added tests for dynamic adoptRootStyles toggling (false→true, true→false)
  • Added test for multiple toggle cycles
  • Added test for theme change interaction with adoptRootStyles

• Updated types.ts

  • Removed outdated warning about runtime changes not working

• Refactored chat/utils.ts

  • Removed duplicate AdoptedStylesController implementation
  • Controller moved to shared controllers directory

Benefits:

• adoptRootStyles now works reactively at runtime (no longer one-time shot)
• Consistent controller implementation across all components
• Improved performance through stylesheet caching
• Better memory management with automatic cleanup
• Proper theme change handling with cache invalidation
• Comprehensive test coverage for all scenarios

Type of Change

• New feature (non-breaking change that adds functionality)

Testing

• Enhanced chat.spec.ts
  • Added ResizeObserver loop error suppression for test stability
  • Added tests for dynamic adoptRootStyles toggling (false→true, true→false)
  • Added test for multiple toggle cycles
  • Added test for theme change interaction with adoptRootStyles

Checklist

• My code follows the project's coding standards
• I have tested my changes locally
• I have updated documentation if needed