refactor(skills): Phase 2.2 - Extract ui5-typescript-expert references

Extracted 3 largest sections to progressive disclosure references:

1. application-code-conversion.md (128 lines)
   - Controller ES6 class patterns
   - Component.ts with IAsyncContentCreation
   - Formatter conversion
   - Event handler typing

2. custom-control-conversion.md (222 lines)
   - MetadataOptions structure
   - Property/aggregation/association typing
   - Renderer conversion patterns
   - Event parameter types

3. version-specific-patterns.md (212 lines)
   - Runtime version detection
   - Conditional event types (>= 1.115.0)
   - IAsyncContentCreation (>= 1.90.0)
   - Test Starter TypeScript patterns

Main skill file:
- Before: 929 lines
- After: 517 lines
- Reduction: -412 lines (-44%)

All sections replaced with essential patterns and references.

Tests: ✅ All structure tests passing

Author: d3xter666