fix(tui): compute truncation budget from actual overhead, not magic numbers

Tags wrapped past pane edge when detail split narrowed the list.
Truncation used fixed constants that didn't account for real tag width.
Now measures everything-except-body and gives body exactly what remains.

internal/tui/cards.go

@@ -340,7 +340,8 @@ func renderCard(e *db.Entity, maxWidth int) string {
 	line := fmt.Sprintf("%s %s%s%s%s", glyph, body, affordStr, extraStr, useStr)
 
 	if maxWidth > 0 && len(stripAnsi(line)) > maxWidth {
-		body = truncate(body, maxWidth-8)
+		overhead := len(stripAnsi(line)) - len([]rune(body))
+		body = truncate(body, maxWidth-overhead)
 		line = fmt.Sprintf("%s %s%s%s%s", glyph, body, affordStr, extraStr, useStr)
 	}