model: add Hy3 (hy_v3) support with MTP speculative decoding (#25395)

* model: add Hy3 (hy_v3) architecture support

Adds Tencent Hunyuan 3 (HF architecture HYV3ForCausalLM, GGUF arch
hy_v3): a MoE decoder stack with per-head Q/K RMSNorm, a sigmoid
router with expert selection bias, an always-active ungated shared
expert, and leading dense block(s) (first_k_dense_replace).

The base implementation is ported from charlie12345's fork
(https://github.com/charlie12345/ROCmFPX, src/models/hyv3.cpp),
adapted to current mainline APIs (hparams.n_layer(), build_qkv,
build_moe_ffn with fused gate_up + scale tensors, output_s).

Note: blk.N.exp_probs_b is stored without a .bias suffix for
compatibility with existing hy_v3 GGUFs produced by that fork.

Co-Authored-By: charlie12345 <charlie12345@users.noreply.github.com>
Co-authored-by: Piotr Wilkin <ilintar@gmail.com>
Assisted-by: Claude Fable 5

common/chat-auto-parser-generator.cpp

@@ -262,6 +262,10 @@ common_peg_parser analyze_tools::build_func_parser(common_chat_peg_builder & p,
     bool              matched_atomic = false;
     common_peg_parser func_parser    = p.eps();
 
+    if (!function.args_separator.empty()) {
+        open = open + p.space() + p.literal(function.args_separator);
+    }
+
     if (!function.name_suffix.empty()) {
         func_parser    = open + call_id_section + p.space() + args;
         matched_atomic = true;