feat(subagent): emit reasoning text as progress in StepCompleted events

src/app/subagent/engine.rs

@@ -416,6 +416,15 @@ pub fn run_subagent(ctx: &SubagentContext, tx: &mpsc::Sender<SubagentEvent>) ->
 
         let content = response.content.clone().unwrap_or_default();
 
+        // Emit thinking/reasoning text as StepCompleted so the parent's
+        // drain thread can show it as progress instead of just the tool name.
+        if !content.is_empty() {
+            let _ = tx.blocking_send(SubagentEvent::StepCompleted {
+                step,
+                output: content.clone(),
+            });
+        }
+
         if has_tool_calls {
             let tool_calls = response.tool_calls.clone().unwrap_or_default();
             // Push the assistant message with tool_calls into the conversation