Radix UI DialogContent accessibility warning

Description
Three dialogs are missing an accessible description, causing Radix UI to emit a console warning and leaving screen reader users without context when a dialog opens. Radix UI's DialogContent requires either a child or an explicit aria-describedby={undefined} opt-out — none of the three affected components provide either.

Steps to reproduce

1. Run the app in dev mode
2. Open any of the three affected dialogs:
   • Command palette (CommandDialog in src/components/ui/command.tsx:29)
   • Webhook setup dialog (WebhookSetupTicketIntegrationDialog in src/components/guides/WebhookSetupTicketIntegrationDialog.tsx:35)
   • Risk scanner dialog (RiskScannerDialog in src/components/RiskScannerDialog.tsx:517)
3. Open the browser console

Expected Behavior
No console warnings. Screen readers announce a meaningful description when focus enters the dialog.

Actual Behavior
Console warning appears:

Warning: Missing `Description` or `aria-describedby={undefined}` for {DialogContent}.

Screen readers receive no description when these dialogs open.

Start with the three locations named in the issue: src/components/ui/command.tsx, src/components/guides/WebhookSetupTicketIntegrationDialog.tsx, and src/components/RiskScannerDialog.tsx. Inspect each DialogContent and run the app in dev mode, opening all three dialogs while watching the browser console. Done means each dialog has a meaningful screen-reader description and the Radix UI warning no longer appears.