feat(tui): add goto modal for slide navigation

- add `GoTo` struct with text input for slide number entry
- implement modal dialog with centered overlay positioning
- add keyboard controls for enter to confirm and esc to cancel
- include input validation for slide number bounds checking
- style modal with rounded borders and help text display

Author: tharropoulos

internal/tui/goto.go

@@ -0,0 +1,142 @@
+package tui
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/charmbracelet/bubbles/textinput"
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/charmbracelet/lipgloss"
+	"github.com/museslabs/kyma/internal/config"
+)
+
+var (
+	gotoModalTitleStyle = lipgloss.NewStyle().
+				MarginBottom(1)
+	gotoModalInputStyle = lipgloss.NewStyle().
+				Border(lipgloss.RoundedBorder()).
+				Padding(0, 1)
+	veryMutedStyle = lipgloss.NewStyle().
+			Foreground(lipgloss.Color("#3C3C3C"))
+	mutedStyle = lipgloss.NewStyle().
+			Foreground(lipgloss.Color("#5C5C5C"))
+)
+
+type GoTo struct {
+	input    textinput.Model
+	choice   int
+	quitting bool
+	maxSlide int
+	showing  bool
+}
+
+func NewGoTo(maxSlides int) GoTo {
+	ti := textinput.New()
+	ti.Placeholder = "Enter slide number..."
+	ti.Focus()
+	ti.CharLimit = 10
+	ti.Width = 20
+
+	return GoTo{
+		input:    ti,
+		choice:   -1,
+		maxSlide: maxSlides,
+	}
+}
+
+func (m GoTo) Init() tea.Cmd {
+	return textinput.Blink
+}
+
+func (m GoTo) Update(msg tea.Msg) (GoTo, tea.Cmd) {
+	var cmd tea.Cmd
+
+	switch msg := msg.(type) {
+	case tea.KeyMsg:
+		switch msg.String() {
+		case "enter":
+			if slideNum, err := strconv.Atoi(m.input.Value()); err == nil && slideNum > 0 {
+				m.choice = slideNum
+			}
+			m.quitting = true
+			m.showing = false
+			return m, tea.Quit
+		case "esc", "ctrl+c":
+			m.quitting = true
+			m.showing = false
+			return m, tea.Quit
+		}
+	}
+
+	m.input, cmd = m.input.Update(msg)
+	return m, cmd
+}
+
+func (m GoTo) View() string {
+	title := gotoModalTitleStyle.Render("Go to Slide")
+
+	input := gotoModalInputStyle.Render(m.input.View())
+
+	enterHelp := lipgloss.JoinHorizontal(
+		lipgloss.Center,
+		mutedStyle.Render("enter"),
+		" ",
+		veryMutedStyle.MarginTop(1).Render("• go"),
+	)
+
+	escHelp := lipgloss.JoinHorizontal(
+		lipgloss.Center,
+		mutedStyle.Render("esc"),
+		" ",
+		veryMutedStyle.MarginTop(1).Render("• cancel"),
+	)
+
+	help := veryMutedStyle.MarginTop(1).Render(
+		lipgloss.JoinHorizontal(lipgloss.Center, enterHelp, "  ", escHelp),
+	)
+
+	maxInfo := mutedStyle.Render(fmt.Sprintf("(1-%d slides available)", m.maxSlide))
+
+	return lipgloss.JoinVertical(
+		lipgloss.Center,
+		title,
+		input,
+		help,
+		maxInfo,
+	)
+}
+
+func (m GoTo) Show(slideView string, width, height int) string {
+	view := m.View()
+	modalContent := lipgloss.NewStyle().
+		Border(lipgloss.RoundedBorder()).
+		BorderForeground(lipgloss.Color(config.DefaultBorderColor)).
+		Padding(3).
+		Render(view)
+
+	_, modalWidth := getLines(modalContent)
+	modalHeight := strings.Count(modalContent, "\n") + 1
+
+	centerX := (width - modalWidth) / 2
+	centerY := (height - modalHeight) / 2
+
+	return placeOverlay(centerX, centerY, modalContent, slideView)
+}
+
+func (m GoTo) IsShowing() bool {
+	return m.showing
+}
+
+func (m GoTo) SetShowing(showing bool) GoTo {
+	m.showing = showing
+	return m
+}
+
+func (m GoTo) Choice() int {
+	return m.choice
+}
+
+func (m GoTo) Quitting() bool {
+	return m.quitting
+}