Fix Qwen3OmniMoe Talker weight loading and config initialization
Author: HuiyingLi
Pull request: yes

# What does this PR do?

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This PR fixes several issues preventing Qwen3OmniMoeForConditionalGeneration from loading and running correctly from the `Qwen/Qwen3-Omni-30B-A3B-Instruct` checkpoint.

# Issues Fixed
Issue: https://github.com/huggingface/transformers/issues/43083
1. Incorrect inherited _tied_weights_keys in Talker
Qwen3OmniMoeTalkerForConditionalGeneration inherits from Qwen3MoeForCausalLM, which defines _tied_weights_keys = {"lm_head.weight": "model.embed_tokens.weight"}. However, the Talker model uses codec_head instead of lm_head and doesn't tie weights. This caused loading errors as the loader expected keys that don't exist in the checkpoint. This causes garbled audio output.
Fix: Override _tied_weights_keys = {} in the Talker class.

2. Incorrect _tp_plan and _pp_plan references
The inherited tensor/pipeline parallelism plans reference lm_head, but the Talker uses codec_head.
Fix: Override with _tp_plan = {"codec_head": "colwise_rep"} and _pp_plan = {"codec_head": (["hidden_states"], ["logits"])}.
3. Missing initializer_range in config classes
Qwen3OmniMoeTalkerConfig, Qwen3OmniMoeCode2WavConfig, and Qwen3OmniMoeConfig were missing the initializer_range attribute. This caused AttributeError during _init_weights() calls.
Fix: Add initializer_range attribute to all affected config classes.


## Who can review?

@zucchini-nlp @ArthurZucker @Cyrilvallez 


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Comments:
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**[For maintainers]** Suggested jobs to run (before merge)

run-slow: qwen3_omni_moe