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-hands/src/hands/mod.rs

@@ -20,6 +20,7 @@ mod researcher;
 mod collector;
 mod clip;
 mod twitter;
+pub mod reminder;
 
 pub use whiteboard::*;
 pub use slideshow::*;
@@ -30,3 +31,4 @@ pub use researcher::*;
 pub use collector::*;
 pub use clip::*;
 pub use twitter::*;
+pub use reminder::*;

crates/zclaw-hands/src/hands/reminder.rs

@@ -0,0 +1,77 @@
+//! Reminder Hand - Internal hand for scheduled reminders
+//!
+//! This is a system hand (id `_reminder`) used by the schedule interception
+//! layer in `agent_chat_stream`. When the NlScheduleParser detects a schedule
+//! intent in chat, it creates a trigger targeting this hand. The SchedulerService
+//! fires the trigger at the scheduled time.
+
+use async_trait::async_trait;
+use serde_json::Value;
+use zclaw_types::Result;
+
+use crate::{Hand, HandConfig, HandContext, HandResult, HandStatus};
+
+/// Internal reminder hand for scheduled tasks
+pub struct ReminderHand {
+    config: HandConfig,
+}
+
+impl ReminderHand {
+    /// Create a new reminder hand
+    pub fn new() -> Self {
+        Self {
+            config: HandConfig {
+                id: "_reminder".to_string(),
+                name: "定时提醒".to_string(),
+                description: "Internal hand for scheduled reminders".to_string(),
+                needs_approval: false,
+                dependencies: vec![],
+                input_schema: None,
+                tags: vec!["system".to_string()],
+                enabled: true,
+                max_concurrent: 0,
+                timeout_secs: 0,
+            },
+        }
+    }
+}
+
+#[async_trait]
+impl Hand for ReminderHand {
+    fn config(&self) -> &HandConfig {
+        &self.config
+    }
+
+    async fn execute(&self, _context: &HandContext, input: Value) -> Result<HandResult> {
+        let task_desc = input
+            .get("task_description")
+            .and_then(|v| v.as_str())
+            .unwrap_or("定时提醒");
+
+        let cron = input
+            .get("cron")
+            .and_then(|v| v.as_str())
+            .unwrap_or("");
+
+        let fired_at = input
+            .get("fired_at")
+            .and_then(|v| v.as_str())
+            .unwrap_or("unknown time");
+
+        tracing::info!(
+            "[ReminderHand] Fired at {} — task: {}, cron: {}",
+            fired_at, task_desc, cron
+        );
+
+        Ok(HandResult::success(serde_json::json!({
+            "task": task_desc,
+            "cron": cron,
+            "fired_at": fired_at,
+            "status": "reminded",
+        })))
+    }
+
+    fn status(&self) -> HandStatus {
+        HandStatus::Idle
+    }
+}