Revert "story-kit: merge 86_story_show_live_activity_status_instead_of_static_thinking_indicator_in_chat"

This reverts commit ef162d91ff.

frontend/src/api/client.ts

@@ -60,7 +60,6 @@ export type WsResponse =
 	  }
 	/** `.story_kit/project.toml` was modified; re-fetch the agent roster. */
 	| { type: "agent_config_changed" };
-	| { type: "tool_activity"; tool_name: string };
 
 export interface ProviderConfig {
 	provider: string;