Fix stall watchdog killing agent during long LLM reasoning turns

Move emitter.touch() before the event filter in spawn_event_forwarder
so streaming events (TextDelta, AssistantTextStart, etc.) also reset
the watchdog timer. Previously these were filtered out, causing the
600s stall watchdog to fire during long generation turns with no
tool calls.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/arc-workflows/src/cli/backend.rs

@@ -43,6 +43,9 @@ fn spawn_event_forwarder(
     let mut rx = session.subscribe();
     tokio::spawn(async move {
         while let Ok(event) = rx.recv().await {
+            // Reset watchdog on every event, including streaming deltas
+            emitter.touch();
+
             // Track file changes from tool calls
             match &event.event {
                 AgentEvent::ToolCallStarted {