feat: modular skill fragments and humanizer-pro variant

## Description
The current skill structure is monolithic, making it difficult to maintain multiple variants (like a Professional mode) without duplication.

## Proposed Solution
- Extract core patterns into src/core_patterns.md.
- Implement a compilation script (sync-adapters.ps1) to assemble variants from fragments.
- Introduce humanizer-pro variant focused on professional/technical contexts.