feat: Task 15 — TUI Tab Framework + Orange Theme

- pkg/tui/styles.go — orange theme palette and component styles
- pkg/tui/tabs.go — Tab interface + TabManager with add/close/next/prev
- pkg/tui/host_list_tab.go — HostListTab implementing Tab interface
- pkg/tui/tui.go — refactored to use TabManager (backward compatible)
- pkg/tui/host_list.go — removed (logic moved to host_list_tab.go)
- pkg/tui/tui_test.go — adapted + added TabManager tests

pkg/tui/styles.go

@@ -0,0 +1,44 @@
+package tui
+
+import "github.com/charmbracelet/lipgloss"
+
+// Orange theme palette
+var (
+	OrangePrimary   = lipgloss.Color("#FF6B00")
+	OrangeSecondary = lipgloss.Color("#FF9F43")
+	OrangeLight     = lipgloss.Color("#FFB800")
+	DarkBg          = lipgloss.Color("#1A1A1A")
+	LightBg         = lipgloss.Color("#2D2D2D")
+	TextPrimary     = lipgloss.Color("#FFFFFF")
+	TextSecondary   = lipgloss.Color("#AAAAAA")
+	GreenSuccess    = lipgloss.Color("#00FF88")
+	RedError        = lipgloss.Color("#FF4444")
+	BlueInfo        = lipgloss.Color("#44AAFF")
+)
+
+// Component styles
+var (
+	TabActiveStyle   = lipgloss.NewStyle().Background(OrangePrimary).Foreground(DarkBg).Bold(true).Padding(0, 2)
+	TabInactiveStyle = lipgloss.NewStyle().Background(LightBg).Foreground(TextSecondary).Padding(0, 2)
+	TabBarStyle      = lipgloss.NewStyle().Background(DarkBg)
+	StatusBarStyle   = lipgloss.NewStyle().Background(OrangePrimary).Foreground(DarkBg).Padding(0, 1)
+	AppTitleStyle    = lipgloss.NewStyle().Foreground(OrangeSecondary).Bold(true)
+	HighlightStyle   = lipgloss.NewStyle().Foreground(OrangePrimary).Bold(true)
+	SelectedStyle    = lipgloss.NewStyle().Foreground(DarkBg).Background(OrangePrimary).Padding(0, 1)
+	ErrorStyle       = lipgloss.NewStyle().Foreground(RedError).Bold(true)
+	SuccessStyle     = lipgloss.NewStyle().Foreground(GreenSuccess).Bold(true)
+	InfoStyle        = lipgloss.NewStyle().Foreground(BlueInfo)
+	SubtitleStyle    = lipgloss.NewStyle().Foreground(TextSecondary)
+	HostNameStyle    = lipgloss.NewStyle().Foreground(OrangeLight).Bold(true)
+	HostDetailStyle  = lipgloss.NewStyle().Foreground(TextSecondary)
+	TagStyle         = lipgloss.NewStyle().Foreground(GreenSuccess)
+	TitleStyle       = AppTitleStyle
+)
+
+// TabWidth returns the width of the tab bar content
+func TabBarWidth(totalWidth int) int {
+	if totalWidth < 10 {
+		return totalWidth
+	}
+	return totalWidth - 2
+}