feat: default system theme (#419)

Co-authored-by: adamdottv <2363879+adamdottv@users.noreply.github.com>

packages/tui/internal/layout/container.go

@@ -3,6 +3,7 @@ package layout
 import (
 	tea "github.com/charmbracelet/bubbletea/v2"
 	"github.com/charmbracelet/lipgloss/v2"
+	"github.com/sst/opencode/internal/styles"
 	"github.com/sst/opencode/internal/theme"
 )
 
@@ -57,7 +58,7 @@ func (c *container) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 
 func (c *container) View() string {
 	t := theme.CurrentTheme()
-	style := lipgloss.NewStyle()
+	style := styles.NewStyle().Background(t.Background())
 	width := c.width
 	height := c.height
 
@@ -66,8 +67,6 @@ func (c *container) View() string {
 		width = c.maxWidth
 	}
 
-	style = style.Background(t.Background())
-
 	// Apply border if any side is enabled
 	if c.borderTop || c.borderRight || c.borderBottom || c.borderLeft {
 		// Adjust width and height for borders