feat(tui): compact log sidebar with severity icons

Replace full viewLogsTab with compact sidebar renderer for the 70/30
monitors split. Single-char severity icons (▼▲◆●·), truncated messages,
no header chrome. Renders directly from engine logs without viewport.

internal/tui/view_dashboard.go

@@ -158,7 +158,8 @@ func (m Model) viewDashboard() string {
 			leftW := availW * 70 / 100
 			rightW := availW - leftW
 			left := lipgloss.NewStyle().Width(leftW).Render(monitors)
-			right := lipgloss.NewStyle().Width(rightW).Render(m.viewLogsTab())
+			sidebar := m.viewLogsSidebar(rightW)
+			right := lipgloss.NewStyle().Width(rightW).Render(sidebar)
 			content = lipgloss.JoinHorizontal(lipgloss.Top, left, right)
 		} else {
 			content = monitors