feat(tui): add summary stats bar below sparse tab tables

Alerts: channel count, type count, total sent, failures.
Nodes: online/total, leader ID, region count.
Maint: active, scheduled, ended counts.

Muted subtitle style — adds useful context without visual noise.

internal/tui/tab_alerts.go

@@ -185,7 +185,7 @@ func (m Model) viewAlertsTab() string {
 	nameW := widths[2]
 	cfgW := widths[4]
 
-	return m.renderTable(
+	tbl := m.renderTable(
 		headers,
 		len(m.alerts),
 		func(start, end int) [][]string {
@@ -206,6 +206,25 @@ func (m Model) viewAlertsTab() string {
 		},
 		widths, nil,
 	)
+
+	var totalSent, totalFail int
+	for _, a := range m.alerts {
+		h := m.engine.GetAlertHealth(a.ID)
+		totalSent += h.SendCount
+		totalFail += h.FailCount
+	}
+	types := make(map[string]bool)
+	for _, a := range m.alerts {
+		types[a.Type] = true
+	}
+	failLabel := "failures"
+	if totalFail == 1 {
+		failLabel = "failure"
+	}
+	summary := fmt.Sprintf("%d channels · %d types · %d sent · %d %s",
+		len(m.alerts), len(types), totalSent, totalFail, failLabel)
+
+	return tbl + "\n  " + m.st.subtleStyle.Render(summary)
 }
 
 func (m Model) viewAlertDetailPanel() string {

internal/tui/tab_maint.go

@@ -107,7 +107,7 @@ func (m Model) viewMaintTab() string {
 	monW := widths[3]
 	timeW := widths[5]
 
-	return m.renderTable(
+	tbl := m.renderTable(
 		headers,
 		len(m.maintenanceWindows),
 		func(start, end int) [][]string {
@@ -130,6 +130,21 @@ func (m Model) viewMaintTab() string {
 		widths,
 		nil,
 	)
+
+	now := time.Now()
+	var active, scheduled, ended int
+	for _, mw := range m.maintenanceWindows {
+		if mw.StartTime.After(now) {
+			scheduled++
+		} else if !mw.EndTime.IsZero() && mw.EndTime.Before(now) {
+			ended++
+		} else {
+			active++
+		}
+	}
+	summary := fmt.Sprintf("%d active · %d scheduled · %d ended", active, scheduled, ended)
+
+	return tbl + "\n  " + m.st.subtleStyle.Render(summary)
 }
 
 func (m *Model) initMaintHuhForm() tea.Cmd {

internal/tui/tab_nodes.go

@@ -1,6 +1,8 @@
 package tui
 
 import (
+	"fmt"
+	"strings"
 	"time"
 )
 
@@ -20,7 +22,7 @@ func (m Model) viewNodesTab() string {
 	}
 	nameW := widths[0]
 
-	return m.renderTable(
+	tbl := m.renderTable(
 		headers,
 		len(m.nodes),
 		func(start, end int) [][]string {
@@ -48,6 +50,30 @@ func (m Model) viewNodesTab() string {
 		widths,
 		nil,
 	)
+
+	var online int
+	regions := make(map[string]bool)
+	var leader string
+	for _, n := range m.nodes {
+		if time.Since(n.LastSeen) < 60*time.Second {
+			online++
+		}
+		if n.Region != "" {
+			regions[n.Region] = true
+		}
+		if n.Name == "leader" {
+			leader = n.ID
+		}
+	}
+	parts := []string{fmt.Sprintf("%d/%d online", online, len(m.nodes))}
+	if leader != "" {
+		parts = append(parts, fmt.Sprintf("leader: %s", leader))
+	}
+	if len(regions) > 0 {
+		parts = append(parts, fmt.Sprintf("%d regions", len(regions)))
+	}
+
+	return tbl + "\n  " + m.st.subtleStyle.Render(strings.Join(parts, " · "))
 }
 
 func (m Model) fmtNodeStatus(lastSeen time.Time) string {