test(coverage): bootstrap vitest unit infra and add tests at 90%+ per file (#1245) (#1269)

* test(coverage): bootstrap vitest unit infra and add tests at 90%+ per file (#1245)

Establishes the unit-test runtime AGENTS.md mandates: a vitest "unit"
project alongside the existing storybook project, RTL + jest-dom +
happy-dom, a Mantine-aware render helper, and a 90%-line per-file
coverage gate enforced by CI. Adds 66 test files covering all 62
components under elements/groups/screens/views, plus core/mcp and
clients/web/src/utils. Total: 577 tests, 98.7% line coverage globally.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* test(coverage): address PR #1269 review feedback

- AGENTS.md: correct coverage gate description (lines ≥ 90, statements ≥ 85,
  functions ≥ 80, branches ≥ 50) with rationale for the relaxed branch
  threshold
- InspectorView.test.tsx: document what the Math.random() mock values
  (0.1 / 0.99) control vs. STUB_SUCCESS_RATE in InspectorView.tsx
- vite.config.ts / tsconfig.test.json: drop unused `globals: true` and the
  `vitest/globals` type now that every test file imports describe/it/expect/vi
  explicitly; manual `afterEach(cleanup)` in setup.ts remains required because
  testing-library auto-cleanup relies on globalThis.afterEach

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

clients/web/src/components/screens/PromptsScreen/PromptsScreen.test.tsx

@@ -0,0 +1,120 @@
+import { describe, it, expect, vi } from "vitest";
+import userEvent from "@testing-library/user-event";
+import type { Prompt } from "@modelcontextprotocol/sdk/types.js";
+import { renderWithMantine, screen } from "../../../test/renderWithMantine";
+import { PromptsScreen } from "./PromptsScreen";
+
+const prompts: Prompt[] = [
+  { name: "summarize", description: "Summarize text" },
+  { name: "translate", description: "Translate text" },
+];
+
+const baseProps = {
+  prompts,
+  listChanged: false,
+  onRefreshList: vi.fn(),
+  onGetPrompt: vi.fn(),
+};
+
+describe("PromptsScreen", () => {
+  it("renders the empty state when no prompt is selected", () => {
+    renderWithMantine(<PromptsScreen {...baseProps} />);
+    expect(
+      screen.getByText("Select a prompt to view details"),
+    ).toBeInTheDocument();
+  });
+
+  it("shows prompt arguments when a prompt is selected", async () => {
+    const user = userEvent.setup();
+    renderWithMantine(<PromptsScreen {...baseProps} />);
+    await user.click(screen.getByText("summarize"));
+    expect(
+      screen.getByRole("button", { name: "Get Prompt" }),
+    ).toBeInTheDocument();
+  });
+
+  it("shows pending state", async () => {
+    const user = userEvent.setup();
+    renderWithMantine(
+      <PromptsScreen {...baseProps} getPromptState={{ status: "pending" }} />,
+    );
+    await user.click(screen.getByText("summarize"));
+    expect(screen.getByText("Loading prompt...")).toBeInTheDocument();
+  });
+
+  it("shows error state", async () => {
+    const user = userEvent.setup();
+    renderWithMantine(
+      <PromptsScreen
+        {...baseProps}
+        getPromptState={{ status: "error", error: "Bad prompt" }}
+      />,
+    );
+    await user.click(screen.getByText("summarize"));
+    expect(screen.getByText("Prompt Error")).toBeInTheDocument();
+    expect(screen.getByText("Bad prompt")).toBeInTheDocument();
+  });
+
+  it("renders fallback error when error message is missing", async () => {
+    const user = userEvent.setup();
+    renderWithMantine(
+      <PromptsScreen {...baseProps} getPromptState={{ status: "error" }} />,
+    );
+    await user.click(screen.getByText("summarize"));
+    expect(screen.getByText("Failed to get prompt")).toBeInTheDocument();
+  });
+
+  it("shows messages when result is provided", async () => {
+    const user = userEvent.setup();
+    renderWithMantine(
+      <PromptsScreen
+        {...baseProps}
+        getPromptState={{
+          status: "ok",
+          result: {
+            messages: [{ role: "user", content: { type: "text", text: "hi" } }],
+          },
+        }}
+      />,
+    );
+    await user.click(screen.getByText("summarize"));
+    expect(screen.getByText("Messages")).toBeInTheDocument();
+  });
+
+  it("updates argument values and calls onGetPrompt", async () => {
+    const user = userEvent.setup();
+    const onGetPrompt = vi.fn();
+    const promptsWithArgs: Prompt[] = [
+      {
+        name: "ask",
+        arguments: [{ name: "topic", required: true }],
+      },
+    ];
+    renderWithMantine(
+      <PromptsScreen
+        {...baseProps}
+        prompts={promptsWithArgs}
+        onGetPrompt={onGetPrompt}
+      />,
+    );
+    await user.click(screen.getByText("ask"));
+    await user.type(screen.getByPlaceholderText("Enter topic..."), "math");
+    await user.click(screen.getByRole("button", { name: "Get Prompt" }));
+    expect(onGetPrompt).toHaveBeenCalledWith("ask", { topic: "math" });
+  });
+
+  it("resets argument values when switching prompts", async () => {
+    const user = userEvent.setup();
+    const promptsWithArgs: Prompt[] = [
+      { name: "alpha", arguments: [{ name: "x" }] },
+      { name: "beta", arguments: [{ name: "y" }] },
+    ];
+    renderWithMantine(
+      <PromptsScreen {...baseProps} prompts={promptsWithArgs} />,
+    );
+    await user.click(screen.getByText("alpha"));
+    await user.type(screen.getByPlaceholderText("Enter x..."), "value");
+    await user.click(screen.getByText("beta"));
+    expect(screen.getByPlaceholderText("Enter y...")).toHaveValue("");
+  });
+});