[TRAIN-5] Example configs are too fragmented; no canonical config per model family

## Problem

The example configs consist of many near-identical recipe files that differ only in minor parallelism settings. There is no canonical config per model family. This makes it difficult to know which config to use as a starting point.

## Suggested fix

Reorganize configs around one canonical recipe per model family (e.g., one for Qwen3.5-0.8B, one for Qwen3.5-9B). Express parallelism choices as documented override examples rather than duplicated config files.