Assign readable ticket keys from project code and sequence.

Replace UUID-looking sync labels in TUI and web with keys like TAS-1,
while keeping the remote UUID for task-master matching.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/ui/views/tickets.go

@@ -177,8 +177,8 @@ func (l *TicketList) renderCard(t ticket.Ticket, selected bool) string {
 
 	badge := l.statusBadge(t.Status)
 	ext := ""
-	if t.ExternalID != "" {
-		ext = lipgloss.NewStyle().Faint(true).Render(t.ExternalID) + " "
+	if id := t.DisplayID(); id != "" {
+		ext = lipgloss.NewStyle().Faint(true).Render(id) + " "
 	}
 	headline := truncateOneLine(plainHeadline(t.Title), max(8, innerWidth-lipgloss.Width(badge)-lipgloss.Width(ext)-2))
 	headerLine := badge + " " + ext + l.Styles.Headline.Render(headline)