feat(tui-go): in-session right panel cycles events / changes / off (d)

Press d (or the "panel" palette command) in-session to cycle the right panel:
- events  — the live event stream (default, unchanged)
- changes — a token-usage line (tokens + turns, summed from the transcript's
            TurnMetrics) over a git-status-style list of files the session has
            written, each with summed +/− from its diff. ^x still opens the full
            diff.
- off     — hide the panel; the output transcript takes the full width.

changesRows derives everything from data already in the model (router-turn
metrics + the tool entries' unified diffs), so no new protocol. Footer + ? help
updated; "changes" preview kind added.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/tui-go/internal/app/demo.go

@@ -22,6 +22,24 @@ func PreviewFrame(kind string, w, h int) string {
 		m.bgUpdates = 3
 		m.selectedID = "04a546aa"
 
+	case "changes":
+		m.connected = true
+		m.currentModel = "llama-cpp:default"
+		m.sessions = sampleSessions()
+		m.selectedID = "04a546aa"
+		m.sessionEntered = true
+		m.rightPanel = 1
+		if s := m.session("04a546aa"); s != nil {
+			s.CurrentStage = "write_script"
+		}
+		m.routerMessages["04a546aa"] = []RouterEntry{
+			{Role: "user", Content: "add a healthcheck script and document it"},
+			{Role: "router", Content: "I'll write the script.", Metrics: &TurnMetrics{LatencyMs: 1200, TotalTokens: 340}},
+			{Role: "tool", Content: "--- a/healthcheck.sh\n+++ b/healthcheck.sh\n@@ -0,0 +1,4 @@\n+#!/usr/bin/env bash\n+curl -sf localhost:8080/health\n+echo ok\n+exit 0\n"},
+			{Role: "router", Content: "Now the docs.", Metrics: &TurnMetrics{LatencyMs: 820, TotalTokens: 150}},
+			{Role: "tool", Content: "--- a/README.md\n+++ b/README.md\n@@ -1,1 +1,2 @@\n existing line\n+## Health\n"},
+		}
+
 	case "compose":
 		m.connected = true
 		m.currentModel = "llama-cpp:default"

apps/tui-go/internal/app/help_complete_test.go

@@ -25,6 +25,7 @@ func TestHelpCoversEveryKeybind(t *testing.T) {
 		"back to the session list",             // l
 		// session
 		"compose a message",                 // i
+		"right panel: events / changes",     // d
 		"toggle chat / steering mode",       // s
 		"show workflows",                    // w
 		"copy the selected message",         // y

apps/tui-go/internal/app/model.go

@@ -278,6 +278,9 @@ type Model struct {
 	diffScrollOffset int
 	modalScroll      int // body scroll for tall fixed-content modals (help, stats)
 	eventStripShown  bool
+	// in-session right panel: 0 = events, 1 = changes (token usage + changed files),
+	// 2 = off (output full-width). Cycled with `d`.
+	rightPanel int
 
 	// artifact viewer (OverlayArtifacts) — populated by the artifact.list response
 	artifacts        []protocol.ArtifactDto

apps/tui-go/internal/app/overlays.go

@@ -830,6 +830,7 @@ func (m Model) helpBody() []string {
 	})
 	section("session", []kb{
 		{"i", "compose a message"},
+		{"d", "right panel: events / changes / off"},
 		{"s", "toggle chat / steering mode"},
 		{"w", "show workflows (idle screen)"},
 		{"y", "copy the selected message (OSC52)"},

apps/tui-go/internal/app/update.go

@@ -310,6 +310,11 @@ func (m Model) handleNormalKey(k tea.KeyMsg) (tea.Model, tea.Cmd) {
 		if ds == StateIdle {
 			m.cycleLauncherWf()
 		}
+	case "d":
+		// In-session: cycle the right panel (events → changes → off).
+		if ds == StateInSession {
+			m.cycleRightPanel()
+		}
 	case "l":
 		if ds != StateIdle {
 			m.sessionEntered = false
@@ -1090,6 +1095,7 @@ func paletteCommands() []paletteCmd {
 		{"grants", "G", "grants", "view / revoke standing grants"},
 		{"statusbar", "", "status bar", "show / hide status-bar segments"},
 		{"rail", "", "idle rail", "show / hide the idle status + keys rail"},
+		{"panel", "d", "right panel", "in-session: events → changes → off"},
 		{"actions", "", "inline actions", "show / hide tool & action rows in output"},
 		{"help", "?", "help", "keybinding cheat-sheet"},
 		{"mode", "s", "toggle mode", "switch chat / steering"},
@@ -1140,6 +1146,8 @@ func (m Model) execPalette(id string) (tea.Model, tea.Cmd) {
 		m.sbIndex = 0
 	case "rail":
 		m.railHidden = !m.railHidden
+	case "panel":
+		m.cycleRightPanel()
 	case "actions":
 		m.toggleInlineActions()
 	case "help":
@@ -1187,6 +1195,11 @@ func (m *Model) cycleLauncherWf() {
 	m.launcherWf = (m.launcherWf + 1) % (len(m.workflows) + 1)
 }
 
+// cycleRightPanel advances the in-session right panel: events → changes → off → events.
+func (m *Model) cycleRightPanel() {
+	m.rightPanel = (m.rightPanel + 1) % 3
+}
+
 func (m *Model) cycleChatMode() {
 	if m.chatMode == ChatModeChat {
 		m.chatMode = ChatModeSteering

apps/tui-go/internal/app/view.go

@@ -261,7 +261,7 @@ func (m Model) renderFooter() string {
 		} else {
 			// Trimmed to fit ~100 cols: tools/stats/model are all reachable via `p cmds`,
 			// so the footer keeps the high-traffic keys + the new transcript nav/copy.
-			hints = []string{hint("i", "message"), hint("^↑↓", "msgs"), hint("y", "copy"), hint("e", "events"), hint("t", "tools"), hint("l", "back"), hint("p", "cmds"), hint("q", "quit")}
+			hints = []string{hint("i", "message"), hint("^↑↓", "msgs"), hint("y", "copy"), hint("e", "events"), hint("d", "panel"), hint("l", "back"), hint("p", "cmds"), hint("q", "quit")}
 		}
 		if m.copiedFlash != 0 && m.frame-m.copiedFlash < copiedFlashFrames {
 			hints = append(hints, lipgloss.NewStyle().Foreground(t.P.OK).Background(bg).Bold(true).Render("✓ copied"))
@@ -295,12 +295,68 @@ func (m Model) renderMain(h int) string {
 	leftW := m.width * 63 / 100
 	rightW := m.width - leftW
 
-	// In-session / approval: output transcript over the event stream.
+	// In-session / approval. The right panel cycles (d): events, changes (token usage +
+	// changed files), or off (output takes the full width).
+	if m.rightPanel == 2 {
+		return m.theme.box("output", m.routerRows(m.width-4, h-2), m.width, h, true)
+	}
 	left := m.theme.box("output", m.routerRows(leftW-4, h-2), leftW, h, true)
-	right := m.theme.box("events", m.eventRows(rightW-4, h), rightW, h, false)
+	var right string
+	if m.rightPanel == 1 {
+		right = m.theme.box("changes", m.changesRows(rightW-4, h), rightW, h, false)
+	} else {
+		right = m.theme.box("events", m.eventRows(rightW-4, h), rightW, h, false)
+	}
 	return lipgloss.JoinHorizontal(lipgloss.Top, left, right)
 }
 
+// changesRows is the in-session "changes" panel: a token-usage line plus a git-status-style
+// list of files the session has written (summed +/- from each write's diff). ^x opens the
+// full diff. Drives the right panel when rightPanel == 1.
+func (m Model) changesRows(w, h int) []string {
+	t := m.theme
+	turns, toks := 0, 0
+	for _, e := range m.routerMessages[m.selectedID] {
+		if e.Role == "router" && e.Metrics != nil {
+			turns++
+			toks += e.Metrics.TotalTokens
+		}
+	}
+	rows := []string{
+		t.span("tokens ", t.P.Faint) + t.span(itoa(toks), t.P.FgStrong) +
+			t.span("  · turns ", t.P.Faint) + t.span(itoa(turns), t.P.Dim),
+		"",
+	}
+
+	type chg struct{ add, del int }
+	var order []string
+	seen := map[string]*chg{}
+	for _, e := range m.routerMessages[m.selectedID] {
+		if e.Role != "tool" || !isUnifiedDiff(e.Content) {
+			continue
+		}
+		p, a, d := diffSummary(e.Content)
+		if seen[p] == nil {
+			seen[p] = &chg{}
+			order = append(order, p)
+		}
+		seen[p].add += a
+		seen[p].del += d
+	}
+	if len(order) == 0 {
+		return append(rows, t.span("no file changes yet", t.P.Faint))
+	}
+	rows = append(rows, t.span("changes  (^x for full diff)", t.P.Faint))
+	for _, p := range order {
+		c := seen[p]
+		icon := lipgloss.NewStyle().Foreground(t.P.Accent2).Background(t.P.Bg).Render("✎ ")
+		delta := lipgloss.NewStyle().Foreground(t.P.OK).Background(t.P.Bg).Render("+"+itoa(c.add)) +
+			t.span(" ", t.P.Bg) + lipgloss.NewStyle().Foreground(t.P.Bad).Background(t.P.Bg).Render("−"+itoa(c.del))
+		rows = append(rows, icon+t.span(truncate(p, w-16), t.P.Fg)+"  "+delta)
+	}
+	return rows
+}
+
 // renderLauncher is the idle screen: a compact, opencode-style input centered in the main
 // area, with a hideable right rail of status + quick keys. The session list isn't shown —
 // it's a keypress away (R). The input's lower-right shows <workflow> · <model>, Tab-cycled.