feat(tui): ntcharts latency line chart in inline detail panel

Replace block-element sparkline with ntcharts streamline chart in the
inline detail panel. Renders a 4-row line chart with thin line style
using the theme accent color. Auto-scales Y axis to latency range.

Added github.com/NimbleMarkets/ntcharts v0.5.1 dependency (lipgloss v1
compatible). Min/Avg/Max stats rendered below the chart.

internal/tui/chart.go

@@ -0,0 +1,31 @@
+package tui
+
+import (
+	"time"
+
+	"github.com/NimbleMarkets/ntcharts/canvas/runes"
+	"github.com/NimbleMarkets/ntcharts/linechart/streamlinechart"
+	"github.com/charmbracelet/lipgloss"
+)
+
+func (m Model) latencyChart(latencies []time.Duration, statuses []bool, width, height int) string {
+	if len(latencies) == 0 || width < 10 || height < 3 {
+		return ""
+	}
+
+	lineStyle := lipgloss.NewStyle().Foreground(m.theme.Accent)
+	slc := streamlinechart.New(width, height,
+		streamlinechart.WithStyles(runes.ThinLineStyle, lineStyle),
+	)
+
+	for i, l := range latencies {
+		ms := float64(l.Milliseconds())
+		if i < len(statuses) && !statuses[i] {
+			ms = 0
+		}
+		slc.Push(ms)
+	}
+	slc.Draw()
+
+	return slc.View()
+}