ui: derive group checkbox state in useToolsPanel

Moves the mixed-state derivation out of the submenu and sheet
snippets into one getGroupCheckState accessor; the snippets just
consume checked and indeterminate.

Assisted-by: pi

tools/ui/src/lib/components/app/chat/ChatForm/ChatFormActions/ChatFormActionAdd/ChatFormActionAddSheet.svelte

@@ -250,11 +250,8 @@
 </div>
 
 {#snippet sheetGroupRow(group: ToolGroup)}
-	{@const checked = toolsPanel.isGroupChecked(group)}
+	{@const checkState = toolsPanel.getGroupCheckState(group)}
 	{@const enabledCount = toolsPanel.getEnabledToolCount(group)}
-	<!-- mixed state: parent on but nothing or only part of it enabled -->
-	{@const indeterminate =
-		group.tools.length > 0 && (enabledCount === 0 ? checked : enabledCount < group.tools.length)}
 	{@const favicon = toolsPanel.getFavicon(group)}
 	{@const groupDisabled = toolsPanel.isGroupDisabled(group)}
 
@@ -281,9 +278,9 @@
 		</span>
 
 		<Checkbox
-			checked={checked && !indeterminate}
+			checked={checkState.checked}
 			class="{ICON_CLASS_DEFAULT} shrink-0"
-			{indeterminate}
+			indeterminate={checkState.indeterminate}
 			onCheckedChange={() => toolsPanel.toggleGroupByKey(group.key)}
 			onclick={(e) => e.stopPropagation()}
 		/>

tools/ui/src/lib/components/app/chat/ChatForm/ChatFormActions/ChatFormActionAdd/ChatFormActionAddToolsSubmenu.svelte

@@ -77,11 +77,7 @@
 
 {#snippet groupRow(group: ToolGroup)}
 	{@const isExpanded = toolsPanel.expandedGroups.has(group.key)}
-	{@const checked = toolsPanel.isGroupChecked(group)}
-	{@const enabledCount = toolsPanel.getEnabledToolCount(group)}
-	<!-- mixed state: parent on but nothing or only part of it enabled -->
-	{@const indeterminate =
-		group.tools.length > 0 && (enabledCount === 0 ? checked : enabledCount < group.tools.length)}
+	{@const checkState = toolsPanel.getGroupCheckState(group)}
 	{@const favicon = toolsPanel.getFavicon(group)}
 	{@const groupDisabled = toolsPanel.isGroupDisabled(group)}
 
@@ -124,9 +120,9 @@
 					{#snippet child({ props })}
 						<Checkbox
 							{...props}
-							checked={checked && !indeterminate}
+							checked={checkState.checked}
 							class="mr-2 {ICON_CLASS_DEFAULT} shrink-0"
-							{indeterminate}
+							indeterminate={checkState.indeterminate}
 							onCheckedChange={() => toolsPanel.toggleGroupByKey(group.key)}
 						/>
 					{/snippet}
@@ -134,7 +130,7 @@
 
 				<Tooltip.Content side="right">
 					<p>
-						{checked ? 'Disable' : 'Enable'}
+						{checkState.checked ? 'Disable' : 'Enable'}
 						{group.tools.length} tool{group.tools.length !== 1 ? 's' : ''}
 					</p>
 				</Tooltip.Content>

tools/ui/src/lib/hooks/use-tools-panel.svelte.ts

@@ -12,6 +12,7 @@ export interface UseToolsPanelReturn {
 	readonly noToolsInfoMessage: string | null;
 	isGroupChecked(group: ToolGroup): boolean;
 	getEnabledToolCount(group: ToolGroup): number;
+	getGroupCheckState(group: ToolGroup): { checked: boolean; indeterminate: boolean };
 	getFavicon(group: ToolGroup): string | null;
 	isGroupDisabled(group: ToolGroup): boolean;
 	isToolEnabled(entry: ToolEntry): boolean;
@@ -65,6 +66,22 @@ export function useToolsPanel(): UseToolsPanelReturn {
 		return group.tools.filter((tool) => conversationsStore.preferences.isToolActive(tool)).length;
 	}
 
+	/**
+	 * Group checkbox state: checked is the parent flag (category on, or the
+	 * server key on for MCP groups); indeterminate marks the mixed case where
+	 * the parent is on but nothing or only part of the group is enabled.
+	 * isToolActive folds the parent gates into the count, so a disabled parent
+	 * always yields plain unchecked.
+	 */
+	function getGroupCheckState(group: ToolGroup): { checked: boolean; indeterminate: boolean } {
+		const checked = isGroupChecked(group);
+		const enabledCount = getEnabledToolCount(group);
+		const indeterminate =
+			group.tools.length > 0 && (enabledCount === 0 ? checked : enabledCount < group.tools.length);
+
+		return { checked, indeterminate };
+	}
+
 	function getFavicon(group: ToolGroup): string | null {
 		if (group.source !== ToolSource.MCP || !group.serverId) return null;
 
@@ -123,6 +140,7 @@ export function useToolsPanel(): UseToolsPanelReturn {
 		expandedGroups,
 		getEnabledToolCount,
 		getFavicon,
+		getGroupCheckState,
 		handleOpen,
 		isGroupChecked,
 		isGroupDisabled,