feat(ui): M4 — agent activity, knowledge search, audit, correlation grouping

Add three new pages completing the control-room web UI:
- Agent activity: polls /agent-activity every 5s, filterable by type/agent
- Knowledge search: FTS over /knowledge/search with snippet + entity links
- Audit trail: browseable audit log with actor/action/entity filters

Enhanced live events page with correlation-id clustering (Groups toggle).
Added fetchAgentActivity/searchKnowledge/fetchAudit to the API client.
11 nav items now cover all planned control-room views.

web/src/lib/utils.ts

@@ -0,0 +1,13 @@
+import { clsx, type ClassValue } from "clsx";
+import { twMerge } from "tailwind-merge";
+
+export function cn(...inputs: ClassValue[]) {
+	return twMerge(clsx(inputs));
+}
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+export type WithoutChild<T> = T extends { child?: any } ? Omit<T, "child"> : T;
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+export type WithoutChildren<T> = T extends { children?: any } ? Omit<T, "children"> : T;
+export type WithoutChildrenOrChild<T> = WithoutChildren<WithoutChild<T>>;
+export type WithElementRef<T, U extends HTMLElement = HTMLElement> = T & { ref?: U | null };