chore(storybook): drop the redundant setProjectAnnotations setup file

Since Storybook 10.3, @storybook/addon-vitest provisions the preview
annotations itself — and *skips* doing so when it finds a setup file
calling setProjectAnnotations. So .storybook/vitest.setup.ts was not
merely redundant, it was actively opting the project out of the
automatic path, which the addon printed a notice about on every run.

Remove the file and the `setupFiles` entry from the `storybook` vitest
project.

A green suite doesn't prove the automatic provisioning works: without
the preview annotations, stories would render outside MantineProvider
and without App.css, and would very likely still pass. Add
src/test/PreviewAnnotations.stories.tsx, which asserts from a play
function that the Mantine theme variables and the App.css tokens are
actually present in the rendered document, so an unthemed render fails
loudly. Verified by emptying `decorators` in preview.tsx and confirming
the story goes red.

The a11y addon's axe runner can't be introspected from a play function,
so it was checked out-of-band: a story with a real violation turned the
suite red with the setup file already removed, confirming
@storybook/addon-a11y/preview is applied automatically.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0119LaPQ3v4NyBK3ZTdM9j84

clients/web/.storybook/vitest.setup.ts

@@ -1,7 +0,0 @@
-import * as a11yAddonAnnotations from "@storybook/addon-a11y/preview";
-import { setProjectAnnotations } from "@storybook/react-vite";
-import * as projectAnnotations from "./preview";
-
-// This is an important step to apply the right configuration when testing your stories.
-// More info at: https://storybook.js.org/docs/api/portable-stories/portable-stories-vitest#setprojectannotations
-setProjectAnnotations([a11yAddonAnnotations, projectAnnotations]);

clients/web/src/test/PreviewAnnotations.stories.tsx

@@ -0,0 +1,78 @@
+import { Button } from "@mantine/core";
+import type { Meta, StoryObj } from "@storybook/react-vite";
+import { expect, within } from "storybook/test";
+import { theme } from "../theme/theme";
+
+// Guard for #1898.
+//
+// `.storybook/vitest.setup.ts` used to call `setProjectAnnotations([...])` to
+// hand the preview annotations to the Storybook vitest project. Since Storybook
+// 10.3 `@storybook/addon-vitest` applies them automatically — and *skips* doing
+// so when it finds such a setup file — so the file was removed and the
+// `setupFiles` entry dropped from the `storybook` project in `vite.config.ts`.
+//
+// A green suite is not evidence that the automatic path works. Two things the
+// setup file used to provision are silently losable:
+//
+//   • `./preview`'s decorator, which wraps every story in `MantineProvider`
+//     with the project theme, and its `import "../src/App.css"`, which defines
+//     the `--inspector-*` tokens. Without them stories render unthemed and
+//     unstyled — and would very likely still pass their play functions.
+//   • `@storybook/addon-a11y/preview`, which runs axe after each play function.
+//     Without it the `a11y: { test: "error" }` parameter is inert and every
+//     story passes its accessibility check vacuously.
+//
+// The story below closes the first gap: it asserts the Mantine theme variables
+// and the `App.css` tokens are actually present in the rendered document, so an
+// unthemed render fails loudly rather than passing. It also asserts the preview
+// `parameters` reached the story, which is the same channel the a11y parameter
+// arrives on. The axe *runner* itself can't be introspected from a play
+// function; it was verified out-of-band by temporarily giving a story a real
+// violation and confirming the suite went red (see the PR for #1898).
+
+// The primary shade the theme pins for the light scheme — the value Mantine
+// derives `--mantine-primary-color-filled` from. Read from the theme rather
+// than hard-coded so a palette change can't silently invalidate the guard.
+const LIGHT_PRIMARY_SHADE = 7;
+
+function expectedPrimaryColor(): string {
+  const palette = theme.colors?.[theme.primaryColor ?? ""];
+  const color = palette?.[LIGHT_PRIMARY_SHADE];
+  if (!color) throw new Error("theme is missing its primary color palette");
+  return color;
+}
+
+const meta: Meta<typeof Button> = {
+  title: "Meta/Preview Annotations",
+  component: Button,
+  args: { children: "Themed" },
+};
+
+export default meta;
+type Story = StoryObj<typeof Button>;
+
+export const ProjectAnnotationsApplied: Story = {
+  play: async ({ canvasElement, parameters }) => {
+    const canvas = within(canvasElement);
+    expect(canvas.getByRole("button", { name: "Themed" })).toBeInTheDocument();
+
+    const root = getComputedStyle(document.documentElement);
+
+    // `MantineProvider` (the `./preview` decorator) injects the theme's CSS
+    // variables onto `:root`. No provider, no variables.
+    expect(root.getPropertyValue("--mantine-primary-color-filled").trim()).toBe(
+      expectedPrimaryColor(),
+    );
+
+    // `--inspector-brand-primary` is defined in `App.css`, which only reaches
+    // the story through `./preview`'s stylesheet import — and it resolves
+    // *through* the Mantine variable above, so this covers both layers.
+    expect(root.getPropertyValue("--inspector-brand-primary").trim()).toBe(
+      expectedPrimaryColor(),
+    );
+
+    // The preview `parameters` merged into the story context — the same channel
+    // that carries `a11y: { test: "error" }` to the a11y addon.
+    expect(parameters.a11y).toMatchObject({ test: "error" });
+  },
+};

clients/web/vite.config.ts

@@ -379,7 +379,15 @@ export default defineConfig(({ command }) => {
                 },
               ],
             },
-            setupFiles: [".storybook/vitest.setup.ts"],
+            // No `setupFiles`: since Storybook 10.3 `@storybook/addon-vitest`
+            // provisions the preview annotations (`.storybook/preview.tsx` plus
+            // `@storybook/addon-a11y/preview`) itself, and *skips* doing so when
+            // it finds a setup file calling `setProjectAnnotations` — so the old
+            // `.storybook/vitest.setup.ts` was both redundant and actively
+            // opting out of the automatic path (#1898). A green suite doesn't
+            // prove the automatic provisioning works (stories rendered without
+            // the Mantine decorator would very likely still pass), so
+            // `src/test/PreviewAnnotations.stories.tsx` asserts it directly.
           },
         },
       ],