feat(tui): stable detail panel height with scroll support

Detail sidebar now maintains consistent height matching the monitors
panel across all modes (default, SLA, history). Content scrolls within
the fixed frame via mouse wheel or j/k when the detail panel is
focused. Scroll offset resets on mode/monitor/period changes. Logs
strip stays visible in all states.

internal/tui/panel.go

@@ -6,16 +6,69 @@ import (
 	"github.com/charmbracelet/lipgloss"
 )
 
-func (m Model) titledPanelH(title, content string, width, height int, focused bool) string {
-	s := m.titledPanel(title, content, width, focused)
+func (m Model) titledPanelH(title, content string, width, height, scrollOffset int, focused bool) string {
 	if height <= 0 {
-		return s
+		return m.titledPanel(title, content, width, focused)
 	}
-	lines := strings.Split(s, "\n")
-	if len(lines) <= height {
-		return s
+
+	borderColor := m.theme.Border
+	titleColor := m.theme.Muted
+	if focused {
+		borderColor = m.theme.Accent
+		titleColor = m.theme.Accent
 	}
-	return strings.Join(lines[:height-1], "\n") + "\n" + lines[len(lines)-1]
+
+	bc := lipgloss.NewStyle().Foreground(borderColor)
+	tc := lipgloss.NewStyle().Foreground(titleColor).Bold(true)
+
+	innerW := width - 2
+	if innerW < 10 {
+		innerW = 10
+	}
+
+	titleRendered := tc.Render(" " + title + " ")
+	titleLen := len([]rune(title)) + 2
+	fillLen := innerW - titleLen - 1
+	if fillLen < 0 {
+		fillLen = 0
+	}
+
+	top := bc.Render("╭─") + titleRendered + bc.Render(strings.Repeat("─", fillLen)+"╮")
+	bottom := bc.Render("╰" + strings.Repeat("─", innerW) + "╯")
+
+	contentStyle := lipgloss.NewStyle().Width(innerW).MaxWidth(innerW)
+	inner := contentStyle.Render(content)
+	contentLines := strings.Split(inner, "\n")
+
+	bodyH := height - 2
+	if bodyH < 1 {
+		bodyH = 1
+	}
+
+	if scrollOffset > len(contentLines)-bodyH {
+		scrollOffset = len(contentLines) - bodyH
+	}
+	if scrollOffset < 0 {
+		scrollOffset = 0
+	}
+
+	end := scrollOffset + bodyH
+	if end > len(contentLines) {
+		end = len(contentLines)
+	}
+	visible := contentLines[scrollOffset:end]
+
+	var lines []string
+	lines = append(lines, top)
+	for _, line := range visible {
+		lines = append(lines, bc.Render("│")+line+strings.Repeat(" ", max(0, innerW-lipgloss.Width(line)))+bc.Render("│"))
+	}
+	for len(lines) < height-1 {
+		lines = append(lines, bc.Render("│")+strings.Repeat(" ", innerW)+bc.Render("│"))
+	}
+	lines = append(lines, bottom)
+
+	return strings.Join(lines, "\n")
 }
 
 func (m Model) titledPanel(title, content string, width int, focused bool) string {