refactor: split termapp into proper internal packages

Replace monolithic internal/termapp with proper separation:
- internal/app: App struct, lifecycle, output loops
- internal/command: CommandHost interface, Dispatcher, handlers
- internal/tui: Model, hotkeys, panels, render (with panelError + border fixes)
- internal/console: RunConsole, escape parsing, entry point logic
- cmd/serialterminal: thin main() calling console.Run()

Eliminate global vars (cfg, sess, out) via dependency injection.
Break App->CommandDispatcher cycle via CommandHost interface.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

internal/tui/render.go

@@ -0,0 +1,190 @@
+package tui
+
+import (
+	"strings"
+
+	"github.com/charmbracelet/lipgloss"
+)
+
+func (m *Model) appendOutput(text string) {
+	if text == "" {
+		return
+	}
+	m.content.WriteString(text)
+	if m.ready {
+		m.viewport.SetContent(m.content.String())
+		if m.followTail {
+			m.viewport.GotoBottom()
+		}
+	}
+}
+
+func (m *Model) renderPrompt() string {
+	lines := []boxLine{
+		{text: m.promptHint, style: modalBodyLineStyle()},
+		{text: m.promptInput.View(), style: modalBodyLineStyle()},
+		{text: "Enter submit | Esc cancel", style: modalFooterLineStyle()},
+	}
+	return renderBox(m.promptTitle, lines, 48, m.availableModalWidth())
+}
+
+func renderModal(title, body string, maxWidth int) string {
+	if title == "" {
+		title = "Info"
+	}
+	parts := strings.Split(strings.ReplaceAll(body, "\r\n", "\n"), "\n")
+	if len(parts) > 12 {
+		parts = append(parts[:12], "... (press Esc/Enter to close)")
+	}
+	lines := make([]boxLine, 0, len(parts))
+	for _, part := range parts {
+		lines = append(lines, boxLine{text: part, style: modalBodyLineStyle()})
+	}
+	return renderBox(title, lines, 20, maxWidth)
+}
+
+func renderPanelModal(title string, lines []panelLine, footer string, maxWidth int) string {
+	boxLines := make([]boxLine, 0, len(lines)+1)
+	for _, line := range lines {
+		style := modalBodyLineStyle()
+		prefix := "  "
+		if line.selected {
+			style = selectedPanelLineStyle()
+			prefix = "▸ "
+		}
+		boxLines = append(boxLines, boxLine{text: prefix + line.text, style: style})
+	}
+	boxLines = append(boxLines, boxLine{text: footer, style: modalFooterLineStyle()})
+	return renderBox(title, boxLines, 40, maxWidth)
+}
+
+func fillScreen(width, height int, content string) string {
+	if width <= 0 || height <= 0 {
+		return content
+	}
+	return lipgloss.Place(width, height, lipgloss.Left, lipgloss.Top, content,
+		lipgloss.WithWhitespaceChars(" "),
+		lipgloss.WithWhitespaceForeground(lipgloss.Color("0")),
+	)
+}
+
+func renderCenteredModal(width, height int, title, body string) string {
+	maxWidth := width - 8
+	if maxWidth < 20 {
+		maxWidth = 20
+	}
+	return renderCenteredModalContent(width, height, renderModal(title, body, maxWidth))
+}
+
+func renderCenteredModalContent(width, height int, content string) string {
+	if width <= 0 || height <= 0 {
+		return content
+	}
+	return lipgloss.Place(width, height, lipgloss.Center, lipgloss.Center, content,
+		lipgloss.WithWhitespaceChars(" "),
+		lipgloss.WithWhitespaceForeground(lipgloss.Color("0")),
+	)
+}
+
+func (m *Model) availableModalWidth() int {
+	if m.width <= 0 {
+		return 100
+	}
+	maxWidth := m.width - 8
+	if maxWidth < 20 {
+		maxWidth = 20
+	}
+	return maxWidth
+}
+
+type boxLine struct {
+	text  string
+	style lipgloss.Style
+}
+
+func renderBox(title string, lines []boxLine, minWidth, maxWidth int) string {
+	contentWidth := lipgloss.Width(title)
+	for _, line := range lines {
+		contentWidth = maxInt(contentWidth, lipgloss.Width(line.text))
+	}
+	contentWidth = maxInt(minWidth, contentWidth)
+	contentWidth = minInt(contentWidth, maxWidth)
+
+	boxStyle := lipgloss.NewStyle().Background(lipgloss.Color("236"))
+	top := boxStyle.Render("╭" + strings.Repeat("─", contentWidth+2) + "╮")
+	bottom := boxStyle.Render("╰" + strings.Repeat("─", contentWidth+2) + "╯")
+
+	rows := make([]string, 0, len(lines)+3)
+	rows = append(rows, top)
+	rows = append(rows, renderBoxRow(modalHeaderLineStyle(), title, contentWidth))
+	for _, line := range lines {
+		rows = append(rows, renderBoxRow(line.style, truncateToWidth(line.text, contentWidth), contentWidth))
+	}
+	rows = append(rows, bottom)
+	return strings.Join(rows, "\n")
+}
+
+func renderBoxRow(contentStyle lipgloss.Style, text string, width int) string {
+	visible := truncateToWidth(text, width)
+	pad := strings.Repeat(" ", maxInt(0, width-lipgloss.Width(visible)))
+	inner := contentStyle.Render(" " + visible + pad + " ")
+	return contentStyle.Render("│" + inner + "│")
+}
+
+func modalHeaderLineStyle() lipgloss.Style {
+	return lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("230")).Background(lipgloss.Color("25"))
+}
+
+func modalBodyLineStyle() lipgloss.Style {
+	return lipgloss.NewStyle().Foreground(lipgloss.Color("252")).Background(lipgloss.Color("236"))
+}
+
+func modalFooterLineStyle() lipgloss.Style {
+	return lipgloss.NewStyle().Foreground(lipgloss.Color("250")).Background(lipgloss.Color("236"))
+}
+
+func selectedPanelLineStyle() lipgloss.Style {
+	return lipgloss.NewStyle().Bold(true).Foreground(lipgloss.Color("230")).Background(lipgloss.Color("31"))
+}
+
+func truncateToWidth(s string, width int) string {
+	if width <= 0 || lipgloss.Width(s) <= width {
+		return s
+	}
+	var b strings.Builder
+	for _, r := range s {
+		next := b.String() + string(r)
+		if lipgloss.Width(next) > width {
+			break
+		}
+		b.WriteRune(r)
+	}
+	return b.String()
+}
+
+func clampIndex(idx, n int) int {
+	if n <= 0 || idx < 0 {
+		return 0
+	}
+	if idx >= n {
+		return n - 1
+	}
+	return idx
+}
+
+func minInt(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+func maxInt(a int, rest ...int) int {
+	max := a
+	for _, v := range rest {
+		if v > max {
+			max = v
+		}
+	}
+	return max
+}