feat: BaseModelConfig + DeepSeekMoE + 工厂模式替代 if/else

- BaseModelConfig: fields() 精确字段匹配 + 类型矫正 + 未知key警告
- DeepSeekMoE: 共享专家 + 路由专家 + top-K 门控
- AttnFactory/FFNFactory: 装饰器注册，DecoderBlock 零分支
- config 用 attn_type/ffn_type 驱动组件选择

astrai/model/components/mlp.py

@@ -1,12 +1,21 @@
+import torch
 import torch.nn as nn
 import torch.nn.functional as F
 from torch import Tensor
 
+from astrai.factory import BaseFactory
 from astrai.model.components.linear import Linear
 
 
+class FFNFactory(BaseFactory[nn.Module]):
+    @classmethod
+    def create(cls, ffn_type: str, dim: int, dim_ffn: int, **kwargs) -> nn.Module:
+        return super().create(ffn_type, dim, dim_ffn, **kwargs)
+
+
+@FFNFactory.register("mlp")
 class MLP(nn.Module):
-    def __init__(self, dim: int, dim_feed_forward: int):
+    def __init__(self, dim: int, dim_feed_forward: int, **kwargs):
         super().__init__()
         self.up = Linear(dim, dim_feed_forward)
         self.gate = Linear(dim, dim_feed_forward)
@@ -16,3 +25,70 @@ class MLP(nn.Module):
         gated = self.up(x) * F.silu(self.gate(x))
         out = self.down(gated)
         return out
+
+
+@FFNFactory.register("moe")
+class DeepSeekMoE(nn.Module):
+    def __init__(
+        self,
+        dim: int,
+        dim_feed_forward: int,
+        n_routed_experts: int,
+        n_shared_experts: int = 1,
+        n_activated_experts: int = 2,
+        topk_method: str = "greedy",
+        **kwargs,
+    ):
+        super().__init__()
+        self.dim = dim
+        self.n_routed_experts = n_routed_experts
+        self.n_shared_experts = n_shared_experts
+        self.n_activated_experts = n_activated_experts
+        self.topk_method = topk_method
+
+        self.router = Linear(dim, n_routed_experts, bias=False)
+
+        self.shared_experts = nn.ModuleList(
+            [MLP(dim, dim_feed_forward) for _ in range(n_shared_experts)]
+        )
+        self.routed_experts = nn.ModuleList(
+            [MLP(dim, dim_feed_forward) for _ in range(n_routed_experts)]
+        )
+
+    def forward(self, x: Tensor) -> Tensor:
+        bsz, seq_len, dim = x.shape
+        x_flat = x.view(-1, dim)
+
+        shared_out = self._shared_forward(x_flat)
+        routed_out = self._routed_forward(x_flat)
+
+        out = (shared_out + routed_out).view(bsz, seq_len, dim)
+        return out
+
+    def _shared_forward(self, x: Tensor) -> Tensor:
+        if self.n_shared_experts == 0:
+            return torch.zeros_like(x)
+        return sum(e(x) for e in self.shared_experts) / self.n_shared_experts
+
+    def _routed_forward(self, x: Tensor) -> Tensor:
+        N, D = x.shape
+        K = self.n_activated_experts
+
+        router_logits = self.router(x)
+        router_probs = torch.softmax(router_logits.float(), dim=-1).to(x.dtype)
+
+        topk_weights, topk_indices = torch.topk(router_probs, K, dim=-1)
+        topk_weights = topk_weights / topk_weights.sum(dim=-1, keepdim=True)
+
+        output = torch.zeros(N, D, device=x.device, dtype=x.dtype)
+        for expert_idx in range(self.n_routed_experts):
+            expert_mask = topk_indices == expert_idx
+            token_idx, k_idx = expert_mask.nonzero(as_tuple=True)
+            if token_idx.numel() == 0:
+                continue
+            expert_input = x[token_idx]
+            expert_output = self.routed_experts[expert_idx](expert_input)
+            weights = topk_weights[token_idx, k_idx].unsqueeze(-1)
+            output.index_add_(0, token_idx, expert_output * weights)
+
+        return output