use tea.View.ProgressBar instead of raw escape codes

Replace manual ConEmu progress bar escape sequences with Bubble Tea v2's
native ProgressBar support on the tea.View struct. This uses the proper
OSC 9;4 sequences via the framework instead of writing raw bytes to
stderr, and automatically handles cleanup when the view changes.

The progress bar state (indeterminate while working) is now set
declaratively in the View() function based on chatPage.IsWorking(),
following the Elm Architecture pattern.

Assisted-By: cagent

Author: dgageot

pkg/tui/page/chat/chat.go

@@ -5,7 +5,6 @@ import (
 	"context"
 	"fmt"
 	"log/slog"
-	"os"
 	"path/filepath"
 	goruntime "runtime"
 	"strings"
@@ -611,8 +610,6 @@ func (p *chatPage) cancelStream(showCancelMessage bool) tea.Cmd {
 	p.msgCancel = nil
 	p.streamCancelled = true
 	p.setPendingResponse(false)
-	p.stopProgressBar()
-
 	// Send StreamCancelledMsg to all components to handle cleanup
 	return tea.Batch(
 		core.CmdHandler(msgtypes.StreamCancelledMsg{ShowMessage: showCancelMessage}),
@@ -853,8 +850,6 @@ func (p *chatPage) processMessage(msg msgtypes.SendMsg) tea.Cmd {
 	// Start working state immediately to show the user something is happening.
 	// This provides visual feedback while the runtime loads tools and prepares the stream.
 	spinnerCmd := p.setWorking(true)
-	p.startProgressBar()
-
 	// Check if this is an agent command that needs resolution
 	// If so, show a loading message with the command description
 	var loadingCmd tea.Cmd
@@ -892,7 +887,6 @@ func (p *chatPage) CompactSession(additionalPrompt string) tea.Cmd {
 }
 
 func (p *chatPage) Cleanup() {
-	p.stopProgressBar()
 	p.sidebar.Cleanup()
 }
 
@@ -999,13 +993,3 @@ func (p *chatPage) BlurMessages() {
 func (p *chatPage) ScrollToBottom() tea.Cmd {
 	return p.messages.ScrollToBottom()
 }
-
-// startProgressBar sets a terminal progress-bar indicator (ConEmu/Windows Terminal).
-// See: https://conemu.github.io/en/AnsiEscapeCodes.html#ConEmu_specific_OSC
-func (p *chatPage) startProgressBar() {
-	fmt.Fprint(os.Stderr, "\x1b]9;4;3;0\x1b\\")
-}
-
-func (p *chatPage) stopProgressBar() {
-	fmt.Fprint(os.Stderr, "\x1b]9;4;0;0\x1b\\")
-}

pkg/tui/page/chat/runtime_events.go

@@ -186,7 +186,6 @@ func (p *chatPage) handleStreamStarted(msg *runtime.StreamStartedEvent) tea.Cmd
 	p.streamCancelled = false
 	spinnerCmd := p.setWorking(true)
 	pendingCmd := p.setPendingResponse(true)
-	p.startProgressBar()
 	sidebarCmd := p.forwardToSidebar(msg)
 	return tea.Batch(pendingCmd, spinnerCmd, sidebarCmd)
 }
@@ -222,7 +221,6 @@ func (p *chatPage) handleStreamStopped(msg *runtime.StreamStoppedEvent) tea.Cmd
 		p.msgCancel = nil
 	}
 	p.streamCancelled = false
-	p.stopProgressBar()
 	sidebarCmd := p.forwardToSidebar(msg)
 
 	// Check if there are queued messages to process

pkg/tui/tui.go

@@ -1891,7 +1891,7 @@ func (m *appModel) View() tea.View {
 	windowTitle := m.windowTitle()
 
 	if m.err != nil {
-		return toFullscreenView(styles.ErrorStyle.Render(m.err.Error()), windowTitle)
+		return toFullscreenView(styles.ErrorStyle.Render(m.err.Error()), windowTitle, false)
 	}
 
 	if !m.ready {
@@ -1901,6 +1901,7 @@ func (m *appModel) View() tea.View {
 				Height(m.wHeight).
 				Render(styles.MutedStyle.Render("Loading…")),
 			windowTitle,
+			false,
 		)
 	}
 
@@ -1957,10 +1958,10 @@ func (m *appModel) View() tea.View {
 		}
 
 		compositor := lipgloss.NewCompositor(allLayers...)
-		return toFullscreenView(compositor.Render(), windowTitle)
+		return toFullscreenView(compositor.Render(), windowTitle, m.chatPage.IsWorking())
 	}
 
-	return toFullscreenView(baseView, windowTitle)
+	return toFullscreenView(baseView, windowTitle, m.chatPage.IsWorking())
 }
 
 // windowTitle returns the terminal window title.
@@ -2136,11 +2137,14 @@ func getEditorDisplayNameFromEnv(visual, editorEnv string) string {
 	return "$EDITOR"
 }
 
-func toFullscreenView(content, windowTitle string) tea.View {
+func toFullscreenView(content, windowTitle string, working bool) tea.View {
 	view := tea.NewView(content)
 	view.AltScreen = true
 	view.MouseMode = tea.MouseModeCellMotion
 	view.BackgroundColor = styles.Background
 	view.WindowTitle = windowTitle
+	if working {
+		view.ProgressBar = tea.NewProgressBar(tea.ProgressBarIndeterminate, 0)
+	}
 	return view
 }