Add a dismissal action for command result cards

Summary

Executing a slash command adds a result card to the conversation. The card looks like a temporary panel, but it has no close or dismiss action.

Repeated command execution causes these cards to accumulate and consume conversation space.

Affected areas

• Slash-command execution
• Command result cards
• Chat conversation timeline

Current behavior

Command result cards remain visible for the lifetime of the current client session.

Users cannot dismiss an individual result or clear accumulated command results without reloading the page.

Expected behavior

Command result cards should provide an accessible dismiss action.

Dismissing a card should remove only the selected ephemeral result without affecting durable conversation messages or the underlying command result.