feat(tui): render entity body as markdown via glamour

Detail pane now pipes entity body through charmbracelet/glamour for
styled markdown output — headers, bold, code blocks, lists. Uses
hardcoded dark style to avoid terminal query freeze in alt screen.

internal/tui/detail.go

@@ -6,6 +6,7 @@ import (
 	"time"
 
 	tea "github.com/charmbracelet/bubbletea"
+	"github.com/charmbracelet/glamour"
 
 	"github.com/lerko/nib/internal/db"
 	"github.com/lerko/nib/internal/display"
@@ -98,7 +99,20 @@ func (d detailModel) previewView(width int) string {
 		b.WriteString("\n")
 	}
 
-	b.WriteString(detailBodyStyle.Render(e.Body))
+	bodyWidth := width - 4
+	if bodyWidth < 20 {
+		bodyWidth = 20
+	}
+	r, _ := glamour.NewTermRenderer(
+		glamour.WithStylePath("dark"),
+		glamour.WithWordWrap(bodyWidth),
+	)
+	rendered, err := r.Render(e.Body)
+	if err != nil {
+		rendered = e.Body
+	}
+	rendered = strings.TrimRight(rendered, "\n")
+	b.WriteString(detailBodyStyle.Render(rendered))
 	b.WriteString("\n")
 
 	if e.CardType != nil {