Fix Qwen3 garbage output: RMSNorm +1 for all Qwen-family models

[unamedkr]

Summary

Fixes Qwen3 0.6B (and likely all Qwen2/2.5/3 non-DeltaNet models) producing garbage output in both native CLI and WASM demo.

Root cause

Qwen's RMSNorm computes output = norm(x) * (1 + weight), not norm(x) * weight. The +1 weight bake-in was only triggered when:

• delta_n_heads > 0 (DeltaNet/Qwen3.5-hybrid), or
• model_type == 1 (Gemma)

Plain Qwen3 has delta_n_heads=0 and model_type=0 → adjustment skipped → activations explode by layer 2 (values reaching 6000+) → garbage tokens.

Fix

Detect Qwen-family models via strstr(gguf->arch, "qwen") using the existing model->gguf_ctx reference. This covers all Qwen variants: qwen2, qwen2moe, qwen3, qwen3_5.

int is_qwen_family = (model->config.delta_n_heads > 0);
if (model->gguf_ctx) {
    const tq_gguf_ctx_t* gctx = (const tq_gguf_ctx_t*)model->gguf_ctx;
    if (strstr(gctx->arch, "qwen") != NULL) is_qwen_family = 1;
}

Impact

Model	Before	After
Qwen3-0.6B	Garbage	Fixed
Qwen2/2.5 (all sizes)	Garbage (if anyone tried)	Fixed
Qwen3.5 (DeltaNet)	Working (delta_n_heads > 0)	Still working
Gemma 3/4	Working (model_type == 1)	Unchanged
Llama/SmolLM/Phi/Mistral	Working (no RMSNorm +1)	Unchanged

Test plan

• Native build passes
• WASM rebuilt with fix
• Qwen3-0.6B WASM demo produces coherent output
• SmolLM2 / Llama 3.2 still work (regression check)

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