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/components/ui/badge/badge.svelte

@@ -0,0 +1,49 @@
+<script lang="ts" module>
+	import { type VariantProps, tv } from "tailwind-variants";
+
+	export const badgeVariants = tv({
+		base: "h-5 gap-1 rounded-4xl border border-transparent px-2 py-0.5 text-xs font-medium transition-all has-data-[icon=inline-end]:pr-1.5 has-data-[icon=inline-start]:pl-1.5 [&>svg]:size-3! focus-visible:border-ring focus-visible:ring-ring/50 aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 aria-invalid:border-destructive group/badge inline-flex w-fit shrink-0 items-center justify-center overflow-hidden whitespace-nowrap transition-colors focus-visible:ring-[3px] [&>svg]:pointer-events-none",
+		variants: {
+			variant: {
+				default: "bg-primary text-primary-foreground [a]:hover:bg-primary/80",
+				secondary: "bg-secondary text-secondary-foreground [a]:hover:bg-secondary/80",
+				destructive: "bg-destructive/10 [a]:hover:bg-destructive/20 focus-visible:ring-destructive/20 dark:focus-visible:ring-destructive/40 text-destructive dark:bg-destructive/20",
+				outline: "border-border text-foreground [a]:hover:bg-muted [a]:hover:text-muted-foreground",
+				ghost: "hover:bg-muted hover:text-muted-foreground dark:hover:bg-muted/50",
+				link: "text-primary underline-offset-4 hover:underline",
+			},
+		},
+		defaultVariants: {
+			variant: "default",
+		},
+	});
+
+	export type BadgeVariant = VariantProps<typeof badgeVariants>["variant"];
+</script>
+
+<script lang="ts">
+	import type { HTMLAnchorAttributes } from "svelte/elements";
+	import { cn, type WithElementRef } from "$lib/utils.js";
+
+	let {
+		ref = $bindable(null),
+		href,
+		class: className,
+		variant = "default",
+		children,
+		...restProps
+	}: WithElementRef<HTMLAnchorAttributes> & {
+		variant?: BadgeVariant;
+	} = $props();
+</script>
+
+<svelte:element
+	this={href ? "a" : "span"}
+	bind:this={ref}
+	data-slot="badge"
+	{href}
+	class={cn(badgeVariants({ variant }), className)}
+	{...restProps}
+>
+	{@render children?.()}
+</svelte:element>