fix(runtime,kernel): HandTool 空壳修复 — 桥接到 HandRegistry 真实执行

B-HAND-1 修复: LLM 调用 hand_quiz/hand_researcher 等 Hand 工具后,
HandTool::execute() 原来返回假成功 JSON, 实际 Hand 并不执行.

修复方案 (沿用 SkillExecutor 模式):
- tool.rs: 新增 HandExecutor trait + ToolContext.hand_executor 字段
- hand_tool.rs: execute() 通过 context.hand_executor 分发到真实执行
- loop_runner.rs: AgentLoop 新增 hand_executor 字段 + builder + 3处 ToolContext 传递
- adapters.rs: 新增 KernelHandExecutor 桥接 HandRegistry.execute()
- kernel/mod.rs: 初始化 KernelHandExecutor + 注册到 AgentLoop
- messaging.rs: 两处 AgentLoop 构建添加 .with_hand_executor()

数据流: LLM tool call → HandTool::execute() → ToolContext.hand_executor
         → KernelHandExecutor → HandRegistry.execute() → Hand trait impl

809 tests passed, 0 failed.

crates/zclaw-kernel/src/kernel/adapters.rs

@@ -3,11 +3,12 @@
 use std::pin::Pin;
 use std::sync::Arc;
 use async_trait::async_trait;
-use serde_json::Value;
+use serde_json::{json, Value};
 
-use zclaw_runtime::{LlmDriver, tool::SkillExecutor};
+use zclaw_runtime::{LlmDriver, tool::{SkillExecutor, HandExecutor}};
 use zclaw_skills::{SkillRegistry, LlmCompleter};
-use zclaw_types::Result;
+use zclaw_hands::HandRegistry;
+use zclaw_types::{AgentId, Result};
 
 /// Adapter that bridges `zclaw_runtime::LlmDriver` -> `zclaw_skills::LlmCompleter`
 pub(crate) struct LlmDriverAdapter {
@@ -134,3 +135,47 @@ impl AgentInbox {
         self.pending.push_back(envelope);
     }
 }
+
+/// Hand executor implementation for Kernel
+///
+/// Bridges `zclaw_runtime::tool::HandExecutor` → `zclaw_hands::HandRegistry`,
+/// allowing `HandTool::execute()` to dispatch to the real Hand implementations.
+pub struct KernelHandExecutor {
+    hands: Arc<HandRegistry>,
+}
+
+impl KernelHandExecutor {
+    pub fn new(hands: Arc<HandRegistry>) -> Self {
+        Self { hands }
+    }
+}
+
+#[async_trait]
+impl HandExecutor for KernelHandExecutor {
+    async fn execute_hand(
+        &self,
+        hand_id: &str,
+        agent_id: &AgentId,
+        input: Value,
+    ) -> Result<Value> {
+        let context = zclaw_hands::HandContext {
+            agent_id: agent_id.clone(),
+            working_dir: None,
+            env: std::collections::HashMap::new(),
+            timeout_secs: 300,
+            callback_url: None,
+        };
+        let result = self.hands.execute(hand_id, &context, input).await?;
+        if result.success {
+            Ok(result.output)
+        } else {
+            Ok(json!({
+                "hand_id": hand_id,
+                "status": "failed",
+                "error": result.error.unwrap_or_else(|| "Unknown hand execution error".to_string()),
+                "output": result.output,
+                "duration_ms": result.duration_ms,
+            }))
+        }
+    }
+}