fix: remove Cancel button from outbound ringing state (#574)

Product decision: agent cannot abort outbound call while ringing.
Risk accepted — misdialled calls will connect before agent can cancel.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/call-desk/active-call-card.tsx

@@ -225,11 +225,9 @@ export const ActiveCallCard = ({ lead, callerPhone, missedCallId, onCallComplete
                         {fullName && <p className="text-sm text-secondary">{phoneDisplay}</p>}
                     </div>
                 </div>
-                <div className="mt-3 flex gap-2">
-                    <Button size="sm" color="primary-destructive" onClick={() => { hangup(); handleReset(); }}>
-                        Cancel
-                    </Button>
-                </div>
+                {/* Cancel button removed per product — risk: agent can't abort
+                    a misdialled outbound call before the customer answers.
+                    <Button size="sm" color="primary-destructive" onClick={() => { hangup(); handleReset(); }}>Cancel</Button> */}
             </div>
         );
     }