fix(chat): align MothershipChat's onContextRemove with the surface contract

The remaining-contexts argument was added to ChatSurfaceContextValue but not to
MothershipChat's own prop type, which forwards straight into it. Nothing passes
the handler there today so it typechecked (fewer params is assignable), but the
two declarations of the same wiring disagreed.

Does not change behavior: home still wires the remove handler only to the
empty-state surface, as it did before this PR.

Author: waleedlatif1

apps/sim/app/workspace/[workspaceId]/home/components/mothership-chat/mothership-chat.tsx

@@ -64,7 +64,12 @@ interface MothershipChatProps {
   userId?: string
   chatId?: string
   onContextAdd?: (context: ChatContext) => void
-  onContextRemove?: (context: ChatContext) => void
+  /**
+   * Receives the input's context list AFTER the removal, so the owner can tell
+   * whether another chip still references the removed chip's resource. Matches
+   * `ChatSurfaceContextValue`, which this forwards to.
+   */
+  onContextRemove?: (context: ChatContext, remaining: ChatContext[]) => void
   onWorkspaceResourceSelect?: (resource: MothershipResource) => void
   draftScopeKey?: string
   layout?: 'mothership-view' | 'copilot-view'