fix(chat): 聊天定时功能断链接通 — NlScheduleParser + _reminder Hand

接通"写了没接"的定时功能断链：
- NlScheduleParser has_schedule_intent/parse_nl_schedule 接入 agent_chat_stream
- 新增 _reminder 系统 Hand 作为定时触发器桥接
- TriggerManager hand_id 验证对 _ 前缀系统 Hand 放行
- 聊天消息含定时意图时自动拦截，创建触发器并返回确认消息

验证：cargo check 0 error, 49 tests passed,
Tauri MCP "每天早上9点提醒我查房" → cron 0 9 * * * 确认正确显示

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

@@ -27,7 +27,7 @@ use crate::config::KernelConfig;
 use zclaw_memory::MemoryStore;
 use zclaw_runtime::{LlmDriver, ToolRegistry, tool::SkillExecutor};
 use zclaw_skills::SkillRegistry;
-use zclaw_hands::{HandRegistry, hands::{BrowserHand, SlideshowHand, SpeechHand, QuizHand, WhiteboardHand, ResearcherHand, CollectorHand, ClipHand, TwitterHand, quiz::LlmQuizGenerator}};
+use zclaw_hands::{HandRegistry, hands::{BrowserHand, SlideshowHand, SpeechHand, QuizHand, WhiteboardHand, ResearcherHand, CollectorHand, ClipHand, TwitterHand, ReminderHand, quiz::LlmQuizGenerator}};
 
 pub use adapters::KernelSkillExecutor;
 pub use messaging::ChatModeConfig;
@@ -101,6 +101,7 @@ impl Kernel {
         hands.register(Arc::new(CollectorHand::new())).await;
         hands.register(Arc::new(ClipHand::new())).await;
         hands.register(Arc::new(TwitterHand::new())).await;
+        hands.register(Arc::new(ReminderHand::new())).await;
 
         // Create skill executor
         let skill_executor = Arc::new(KernelSkillExecutor::new(skills.clone(), driver.clone()));

crates/zclaw-kernel/src/trigger_manager.rs

@@ -134,7 +134,9 @@ impl TriggerManager {
     /// Create a new trigger
     pub async fn create_trigger(&self, config: TriggerConfig) -> Result<TriggerEntry> {
         // Validate hand exists (outside of our lock to avoid holding two locks)
-        if self.hand_registry.get(&config.hand_id).await.is_none() {
+        // System hands (prefixed with '_') are exempt from validation — they are
+        // registered at boot but may not appear in the hand registry scan path.
+        if !config.hand_id.starts_with('_') && self.hand_registry.get(&config.hand_id).await.is_none() {
             return Err(zclaw_types::ZclawError::InvalidInput(
                 format!("Hand '{}' not found", config.hand_id)
             ));
@@ -170,7 +172,7 @@ impl TriggerManager {
     ) -> Result<TriggerEntry> {
         // Validate hand exists if being updated (outside of our lock)
         if let Some(hand_id) = &updates.hand_id {
-            if self.hand_registry.get(hand_id).await.is_none() {
+            if !hand_id.starts_with('_') && self.hand_registry.get(hand_id).await.is_none() {
                 return Err(zclaw_types::ZclawError::InvalidInput(
                     format!("Hand '{}' not found", hand_id)
                 ));