fix(tui): add ANSI-16 color fallbacks for SSH terminals

Theme colors now use lipgloss.CompleteColor with hand-picked ANSI-16
values instead of raw hex. Prevents algorithmic degradation from
collapsing dark backgrounds into indistinguishable ANSI colors over
SSH. Backgrounds fall through to terminal default in 16-color mode;
semantic colors map to distinct ANSI indices (green/yellow/red/blue/
cyan/magenta). TrueColor rendering is unchanged.

internal/tui/view_detail.go

@@ -215,7 +215,7 @@ func (m Model) viewDetailPanel() string {
 
 	b.WriteString(m.divider() + "\n")
 	if site.Type == "push" {
-		b.WriteString("  " + m.zones.Mark("spark-heartbeat", m.heartbeatSparkline(hist.Statuses, detailSparkWidth, "")))
+		b.WriteString("  " + m.zones.Mark("spark-heartbeat", m.heartbeatSparkline(hist.Statuses, detailSparkWidth, nil)))
 		if len(hist.Statuses) > 0 {
 			up := 0
 			for _, s := range hist.Statuses {
@@ -228,7 +228,7 @@ func (m Model) viewDetailPanel() string {
 				up, len(hist.Statuses))
 		}
 	} else {
-		b.WriteString("  " + m.zones.Mark("spark-latency", m.latencySparkline(hist.Latencies, hist.Statuses, detailSparkWidth, "")))
+		b.WriteString("  " + m.zones.Mark("spark-latency", m.latencySparkline(hist.Latencies, hist.Statuses, detailSparkWidth, nil)))
 		var minL, maxL, total time.Duration
 		count := 0
 		for i, l := range hist.Latencies {