Add standard ESPnet configuration for download counting

Publish the existing ESPnet configuration as config.yaml so normal repository downloads include a Hugging Face download-counting query file. Document the configuration filename and preserve release integrity checks.

config.yaml

@@ -0,0 +1,57 @@
+job_type: speechlm
+
+# Reconstructed config that reproduces the model behind the public
+# stage-2 pretrained BASE checkpoint (exp/opuslm_v2_stage2_pretrain_base,
+# step 260000). The original launch script referenced this filename but it
+# was never committed; recreated here as the base-tokenizer analog of
+# conf/train_stage2_qwen3.yaml (Qwen3-8B-Base backbone/tokenizer).
+# Vocab check: 256 special + 151936 (Qwen3-8B-Base) + 8200 (Xcodec 8x1025)
+# = 160392 = embed_tokens rows in the checkpoint.
+
+multimodal_io:
+    text:
+        tokenizer_name: Qwen/Qwen3-8B-Base
+    discrete_audio:
+        codec_choice: Xcodec
+        codec_hf_model_tag: hf-audio/xcodec-hubert-general
+        ssl_choice: null
+        ssl_hf_model_tag: null
+        delay_interleave: true
+        stream_weights: [0.125, 0.125, 0.125, 0.125, 0.125, 0.125, 0.125, 0.125]
+    continuous_audio:
+        encoder_choice: huggingface
+        encoder_hf_model_tag: Qwen/Qwen3-Omni-30B-A3B-Instruct
+        attn_implementation: flash_attention_3
+        dtype: bfloat16
+
+model:
+    model_choice: parallel
+    model_hf_tag: Qwen/Qwen3-8B-Base
+    model_conf:
+        attn_implementation: flash_attention_3
+        dtype: bfloat16
+        # NOTE: compile_transformer_body / freeze_text_embeddings appear in the
+        # original stage configs but are dead keys in the current espnet2/speechlm
+        # code (referenced nowhere). transformers 5.x silently drops them; 4.57.x
+        # forwards them into the HF constructor and crashes. Omitted here.
+    activation_checkpointing: true
+
+preprocessor:
+    audio_input: continuous_audio
+    audio_output: discrete_audio
+    loss_region: assistant
+    audio_cfg: 0.05
+
+data_loading:
+    batchfy_method: pack
+    batch_size: 15000
+    save_loader_state: false
+    seed: 43
+    num_workers: 6
+
+trainer:
+    deepspeed_config: conf/deepspeed_stage2.json
+    freeze_param: [multimodal_io_dict.discrete_audio, multimodal_io_dict.continuous_audio]
+    max_step: 700000
+    save_interval: 5000
+    log_interval: 1