Integrates DeepSeek's Engram (N-gram hash lookup + context-aware gating
+ depthwise causal conv) as an optional module behind --engram CLI flag.
Placed at two layers per paper ablation findings (layer 1 and n_layer//2-1).
Coexists with existing Value Embeddings; disabled by default.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
