eat(AliasDataFrameRDF): RDataFrame integration prototype

- AST-based expression conversion (numpy → C++)
- Topological sort for dependency-ordered Define() calls
- Tree setup mirroring LoadADFTree() (friend trees + indices)
- Research tests confirming RDataFrame friend tree support

All 35 tests passing including indexed friend and composite index.

Prepares for RNTuple migration (TTree::Draw deprecated).

Co-authored-by: GPT (Performance Review)
Co-authored-by: Gemini (C++/ROOT Review)
Reviewed-by: Claude (Architect)

Author: miranov25