feat: sub-agent streaming progress — TaskTool emits real-time status events

- Rust: LoopEvent::SubtaskStatus variant added to loop_runner.rs
- Rust: ToolContext.event_sender field for streaming tool progress
- Rust: TaskTool emits started/running/completed/failed via event_sender
- Rust: StreamChatEvent::SubtaskStatus mapped in Tauri chat command
- TS: StreamEventSubtaskStatus type + onSubtaskStatus callback added
- TS: kernel-chat.ts handles subtaskStatus event from Tauri
- TS: streamStore.ts wires callback, maps backend→frontend status,
  updates assistant message subtasks array in real-time

crates/zclaw-runtime/src/tool.rs

@@ -4,9 +4,11 @@ use std::collections::HashMap;
 use std::sync::Arc;
 use async_trait::async_trait;
 use serde_json::Value;
+use tokio::sync::mpsc;
 use zclaw_types::{AgentId, Result};
 
 use crate::driver::ToolDefinition;
+use crate::loop_runner::LoopEvent;
 use crate::tool::builtin::PathValidator;
 
 /// Tool trait for implementing agent tools
@@ -80,6 +82,9 @@ pub struct ToolContext {
     pub skill_executor: Option<Arc<dyn SkillExecutor>>,
     /// Path validator for file system operations
     pub path_validator: Option<PathValidator>,
+    /// Optional event sender for streaming tool progress to the frontend.
+    /// Tools like TaskTool use this to emit sub-agent status events.
+    pub event_sender: Option<mpsc::Sender<LoopEvent>>,
 }
 
 impl std::fmt::Debug for ToolContext {
@@ -90,6 +95,7 @@ impl std::fmt::Debug for ToolContext {
             .field("session_id", &self.session_id)
             .field("skill_executor", &self.skill_executor.as_ref().map(|_| "SkillExecutor"))
             .field("path_validator", &self.path_validator.as_ref().map(|_| "PathValidator"))
+            .field("event_sender", &self.event_sender.as_ref().map(|_| "Sender<LoopEvent>"))
             .finish()
     }
 }
@@ -102,6 +108,7 @@ impl Clone for ToolContext {
             session_id: self.session_id.clone(),
             skill_executor: self.skill_executor.clone(),
             path_validator: self.path_validator.clone(),
+            event_sender: self.event_sender.clone(),
         }
     }
 }