feat(skills): SemanticSkillRouter — TF-IDF + Embedding 混合路由

实现 SemanticSkillRouter 核心模块 (zclaw-skills):
- Embedder trait + NoOpEmbedder (TF-IDF fallback)
- SkillTfidfIndex 全文索引
- retrieve_candidates() Top-K 检索
- route() 置信度阈值路由 (0.85)
- cosine_similarity 公共函数
- 单元测试覆盖

Kernel 适配层 (zclaw-kernel):
- EmbeddingAdapter: zclaw-growth EmbeddingClient → Embedder

文档同步:
- 01-intelligent-routing.md Phase 1+2 标记完成

crates/zclaw-kernel/src/skill_router.rs

@@ -0,0 +1,25 @@
+//! Skill router integration for the Kernel
+//!
+//! Bridges zclaw-growth's `EmbeddingClient` to zclaw-skills' `Embedder` trait,
+//! enabling the `SemanticSkillRouter` to use real embedding APIs.
+
+use std::sync::Arc;
+use async_trait::async_trait;
+
+/// Adapter: zclaw-growth EmbeddingClient → zclaw-skills Embedder
+pub struct EmbeddingAdapter {
+    client: Arc<dyn zclaw_runtime::EmbeddingClient>,
+}
+
+impl EmbeddingAdapter {
+    pub fn new(client: Arc<dyn zclaw_runtime::EmbeddingClient>) -> Self {
+        Self { client }
+    }
+}
+
+#[async_trait]
+impl zclaw_skills::semantic_router::Embedder for EmbeddingAdapter {
+    async fn embed(&self, text: &str) -> Option<Vec<f32>> {
+        self.client.embed(text).await.ok()
+    }
+}