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/ticket/ticket.go

@@ -68,9 +68,22 @@ type Ticket struct {
 	CreatedAt   time.Time `json:"createdAt"`
 	UpdatedAt   time.Time `json:"updatedAt"`
 
+	// Readable key assigned by the server (e.g. "ABC-42"). Optional on local-only tickets.
+	Number int    `json:"number,omitempty"`
+	Key    string `json:"key,omitempty"`
+
 	// External sync (optional). Local UUID stays in ID.
 	Source      string    `json:"source,omitempty"`
 	ExternalID  string    `json:"externalId,omitempty"`
 	ExternalURL string    `json:"externalUrl,omitempty"`
 	SyncedAt    time.Time `json:"syncedAt,omitempty"`
 }
+
+// DisplayID returns the human-readable ticket label for UI.
+// Prefers the server key; falls back to ExternalID (e.g. YouTrack idReadable).
+func (t Ticket) DisplayID() string {
+	if t.Key != "" {
+		return t.Key
+	}
+	return t.ExternalID
+}