Update: JSDoc documentation for core entry points (fixes #827)

[joe-replin]

Update

• Fixes JSDocs - Core Entry Points #827
• Adds JSDoc documentation comments to six core framework files
• Documents all public methods with parameter types, return values, and examples
• Includes file-level documentation explaining architecture and usage patterns

Testing

1. Open any of the following files in VS Code or another JSDoc-compatible editor:
   • adapt.js
   • app.js
   • components.js
   • data.js
   • router.js
   • startController.js
2. Hover over a method name (e.g., router.navigateToElement) to see the tooltip documentation
3. When calling a method, verify autocomplete suggests parameters with type information