This is a major milestone toward intelligent data handling.

• chunker.ts: Text chunking with precision split control
• markdown-splitter.ts: Intelligent Markdown-aware splitting
• cosine-similarity.ts: Semantic similarity calculator
• Test suite updated for full coverage of these features
• tsconfig.json modified to explicitly include test paths

+ New: `chunker`, `cosine-similarity`, `markdown-splitter` in `src/core/`
+ New tests: `chunker.test.ts`, `md-splitter.test.ts`
~ Updated exports via `src/core/index.ts`
~ `tsconfig.json` includes `src/tests`