🚨 Replace deprecated style copy

The `lipgloss` package has [deprecated][1] the use of style copying
using the `Copy` method.

The documentation has been updated to provide an alternative approach:

> to copy just use assignment (i.e. a := b). All methods also return a
> new style.

This change applies the recommendation.

[1]: charmbracelet/lipgloss#289

internal/ui/body/style.go

@@ -32,7 +32,7 @@ func defaultStyles(th theme.Theme) Styles {
 		BorderForeground(clr.Boundary).
 		Padding(0, 1, 0, 1)
 
-	s.focusBoundary = s.boundary.Copy().
+	s.focusBoundary = s.boundary.
 		BorderForeground(clr.FocusBoundary)
 
 	s.textAreaPlaceholder = lipgloss.NewStyle().

internal/ui/filterlist/style.go

@@ -41,7 +41,7 @@ func defaultStyles(th theme.Theme) Styles {
 		BorderStyle(lipgloss.NormalBorder()).
 		BorderForeground(clr.Boundary)
 
-	s.focusBoundary = s.boundary.Copy().
+	s.focusBoundary = s.boundary.
 		BorderForeground(clr.FocusBoundary)
 
 	s.paginatorBoundary = lipgloss.NewStyle().

internal/ui/header/style.go

@@ -52,7 +52,7 @@ func defaultStyles(th theme.Theme) Styles {
 		BorderStyle(lipgloss.NormalBorder()).
 		BorderForeground(clr.EmojiBoundary)
 
-	s.emojiFocusBoundary = s.emojiBoundary.Copy().
+	s.emojiFocusBoundary = s.emojiBoundary.
 		BorderForeground(clr.EmojiFocusBoundary)
 
 	s.summaryBoundary = lipgloss.NewStyle().
@@ -64,7 +64,7 @@ func defaultStyles(th theme.Theme) Styles {
 		BorderStyle(lipgloss.NormalBorder()).
 		BorderForeground(clr.SummaryBoundary)
 
-	s.summaryFocusBoundary = s.summaryBoundary.Copy().
+	s.summaryFocusBoundary = s.summaryBoundary.
 		BorderForeground(clr.SummaryFocusBoundary)
 
 	s.counterDivider = lipgloss.NewStyle().

internal/ui/option/theme/style.go

@@ -28,7 +28,7 @@ func defaultStyles(th theme.Theme) Styles {
 		Padding(0, 1, 0, 1).
 		MarginBottom(1)
 
-	s.themeTitleFocus = s.themeTitle.Copy().
+	s.themeTitleFocus = s.themeTitle.
 		BorderForeground(clr.TitleFocus)
 
 	s.themeTitleLabel = lipgloss.NewStyle().
@@ -43,7 +43,7 @@ func defaultStyles(th theme.Theme) Styles {
 		Width(40).
 		BorderForeground(clr.Boundary)
 
-	s.themeListBoundaryFocus = s.themeListBoundary.Copy().
+	s.themeListBoundaryFocus = s.themeListBoundary.
 		BorderForeground(clr.BoundaryFocus)
 
 	return s