pan-theme-provider
Manages theme state and automatically responds to system light/dark mode preferences.
Broadcasts theme changes via PAN for coordinated updates across components.
Usage:

Events emitted via PAN:
- theme.changed: { theme: 'light' | 'dark' | 'auto', effective: 'light' | 'dark' }
- theme.system-changed: { theme: 'light' | 'dark' }
Attributes:
- theme: 'light' | 'dark' | 'auto' (default: 'auto')

Class: PanThemeProvider

pan-theme-provider
Manages theme state and automatically responds to system light/dark mode preferences.
Broadcasts theme changes via PAN for coordinated updates across components.
Usage:

Events emitted via PAN:
- theme.changed: { theme: 'light' | 'dark' | 'auto', effective: 'light' | 'dark' }
- theme.system-changed: { theme: 'light' | 'dark' }
Attributes:
- theme: 'light' | 'dark' | 'auto' (default: 'auto')