Add config.json (architecture params, verified 6,162,688 params)

config.json

@@ -4,11 +4,13 @@
   "d_model": 256,
   "n_layers": 4,
   "n_heads": 4,
-  "ffn_dim": 640,
-  "max_position_embeddings": 512,
+  "head_dim": 64,
+  "ff_dim": 640,
+  "context_length": 512,
   "tie_word_embeddings": true,
-  "rms_norm": true,
-  "rope": true,
-  "swiglu": true,
-  "num_parameters": 6162688
+  "norm_eps": 1e-05,
+  "rope_base": 10000.0,
+  "n_params": 6162688,
+  "dtype": "float32",
+  "note": "Custom LLaMA-style architecture (RoPE + causal SDPA + SwiGLU + RMSNorm pre-norm). Not transformers-native; load via the provided train_compactlm5m.py CompactLM class or a matching custom loader."
 }