Make /compact non-blocking with spinner feedback

Run session compaction asynchronously in a background goroutine instead
of blocking the TUI render thread. Show the working spinner and pending
response indicator while the LLM generates the summary, and clear them
when the compaction completes. The compaction context is cancellable via
Esc, matching the behavior of regular agent streams.

Fixes #1678

Assisted-By: cagent

Author: dgageot

pkg/app/app.go

@@ -717,15 +717,21 @@ func (a *App) ShouldExitAfterFirstResponse() bool {
 	return a.exitAfterFirstResponse
 }
 
-func (a *App) CompactSession(additionalPrompt string) {
-	if a.session != nil {
+func (a *App) CompactSession(ctx context.Context, additionalPrompt string) {
+	if a.session == nil {
+		return
+	}
+
+	go func() {
 		events := make(chan runtime.Event, 100)
-		a.runtime.Summarize(context.Background(), a.session, additionalPrompt, events)
-		close(events)
+		go func() {
+			defer close(events)
+			a.runtime.Summarize(ctx, a.session, additionalPrompt, events)
+		}()
 		for event := range events {
-			a.events <- event
+			a.sendEvent(ctx, event)
 		}
-	}
+	}()
 }
 
 func (a *App) PlainTextTranscript() string {

pkg/tui/page/chat/chat.go

@@ -1155,11 +1155,18 @@ func (p *chatPage) processMessage(msg msgtypes.SendMsg) tea.Cmd {
 // CompactSession generates a summary and compacts the session history
 func (p *chatPage) CompactSession(additionalPrompt string) tea.Cmd {
 	// Cancel any active stream without showing cancellation message
-	p.cancelStream(false)
+	cancelCmd := p.cancelStream(false)
 
-	p.app.CompactSession(additionalPrompt)
+	var ctx context.Context
+	ctx, p.msgCancel = context.WithCancel(context.Background())
+	p.app.CompactSession(ctx, additionalPrompt)
 
-	return p.messages.ScrollToBottom()
+	return tea.Batch(
+		cancelCmd,
+		p.setWorking(true),
+		p.setPendingResponse(true),
+		p.messages.ScrollToBottom(),
+	)
 }
 
 func (p *chatPage) Cleanup() {

pkg/tui/page/chat/runtime_events.go

@@ -124,7 +124,12 @@ func (p *chatPage) handleRuntimeEvent(msg tea.Msg) (bool, tea.Cmd) {
 
 	case *runtime.SessionCompactionEvent:
 		if msg.Status == "completed" {
-			return true, notification.SuccessCmd("Session compacted successfully.")
+			return true, tea.Batch(
+				p.setWorking(false),
+				p.setPendingResponse(false),
+				notification.SuccessCmd("Session compacted successfully."),
+				p.messages.ScrollToBottom(),
+			)
 		}
 		return true, nil