feat: add workspace filter for shared workspaces (#21310)

resolves coder/internal#1129

<img width="361" height="462" alt="Screenshot 2025-12-17 at 20 49 07"
src="https://github.com/user-attachments/assets/e06843f0-15e4-41fc-b736-ccfaa303ee74"
/>

site/src/pages/WorkspacesPage/filter/WorkspacesFilter.stories.tsx

@@ -0,0 +1,81 @@
+import { mockApiError } from "testHelpers/entities";
+import { withDashboardProvider } from "testHelpers/storybook";
+import type { Meta, StoryObj } from "@storybook/react-vite";
+import {
+	getDefaultFilterProps,
+	MockMenu,
+} from "components/Filter/storyHelpers";
+import type { WorkspaceFilterState } from "./WorkspacesFilter";
+import { WorkspacesFilter } from "./WorkspacesFilter";
+
+const defaultFilterProps = getDefaultFilterProps<WorkspaceFilterState>({
+	query: "owner:me",
+	menus: {
+		user: MockMenu,
+		template: MockMenu,
+		status: MockMenu,
+		organizations: MockMenu,
+	},
+	values: {
+		owner: "me",
+		template: undefined,
+		status: undefined,
+	},
+});
+
+const meta: Meta<typeof WorkspacesFilter> = {
+	title: "pages/WorkspacesPage/WorkspacesFilter",
+	component: WorkspacesFilter,
+	args: {
+		filter: defaultFilterProps.filter,
+		error: undefined,
+		templateMenu: MockMenu,
+		statusMenu: MockMenu,
+	},
+	decorators: [withDashboardProvider],
+};
+
+export default meta;
+type Story = StoryObj<typeof WorkspacesFilter>;
+
+export const Default: Story = {};
+
+export const WithUserMenu: Story = {
+	args: {
+		userMenu: MockMenu,
+	},
+};
+
+export const WithOrganizations: Story = {
+	args: {
+		userMenu: MockMenu,
+		organizationsMenu: MockMenu,
+	},
+	parameters: {
+		showOrganizations: true,
+	},
+};
+
+export const Loading: Story = {
+	args: {
+		statusMenu: {
+			...MockMenu,
+			isInitializing: true,
+		},
+	},
+};
+
+export const WithError: Story = {
+	args: {
+		error: mockApiError({
+			message: "Invalid filter query",
+			validations: [{ field: "filter", detail: "Invalid filter syntax" }],
+		}),
+	},
+};
+
+export const WithDormantPreset: Story = {
+	parameters: {
+		features: ["advanced_template_scheduling"],
+	},
+};

site/src/pages/WorkspacesPage/filter/WorkspacesFilter.tsx

@@ -29,6 +29,7 @@ const workspaceFilterQuery = {
 	failed: "status:failed",
 	dormant: "dormant:true",
 	outdated: "outdated:true",
+	shared: "shared:true",
 };
 
 type FilterPreset = {
@@ -59,6 +60,10 @@ const PRESET_FILTERS: FilterPreset[] = [
 		query: workspaceFilterQuery.outdated,
 		name: "Outdated workspaces",
 	},
+	{
+		query: workspaceFilterQuery.shared,
+		name: "Shared workspaces",
+	},
 ];
 
 // Defined outside component so that the array doesn't get reconstructed each render