ui: make Settings tools tab edit defaults with category toggles

Adds per-category checkboxes and a caption stating the tab applies
to new conversations; tool picks inside a chat only affect that
chat.

Assisted-by: pi

tools/ui/src/lib/components/app/settings/SettingsChat/SettingsChatToolsTab.svelte

@@ -25,6 +25,10 @@
 	<div class="py-8 text-center text-sm text-muted-foreground">No tools available</div>
 {:else}
 	<div class="space-y-2">
+		<p class="text-sm text-muted-foreground">
+			Applies to new conversations. Tool picks inside a chat only affect that chat.
+		</p>
+
 		{#each groups as group (group.key)}
 			{@const isExpanded = expandedGroups.has(group.key)}
 			<Collapsible.Root onOpenChange={() => toggleExpanded(group.key)} open={isExpanded}>
@@ -37,6 +41,17 @@
 						<ChevronRight class="h-3.5 w-3.5 shrink-0" />
 					{/if}
 
+					{@const isCategoryEnabled =
+						group.source !== ToolSource.MCP && toolsStore.isCategoryEnabled(group.source)}
+
+					{#if group.source !== ToolSource.MCP}
+						<Checkbox
+							checked={isCategoryEnabled}
+							onCheckedChange={() => toolsStore.toggleCategory(group.source)}
+							onclick={(e) => e.stopPropagation()}
+						/>
+					{/if}
+
 					{@const faviconUrl = group.serverId ? mcpStore.getServerFavicon(group.serverId) : null}
 
 					<span class="inline-flex min-w-0 items-center gap-1.5 font-medium">