test: use extends: true for Vitest projects, guard clipboard spy target

src/lib/components/CopyButton.svelte.test.ts

@@ -1,4 +1,4 @@
-import { beforeEach, describe, expect, it, vi } from "vitest";
+import { beforeAll, beforeEach, describe, expect, it, vi } from "vitest";
 import { render } from "vitest-browser-svelte";
 import CopyButton from "./CopyButton.svelte";
 
@@ -6,6 +6,17 @@ import CopyButton from "./CopyButton.svelte";
 // grant clipboard-read permission, and the component's contract is "calls
 // navigator.clipboard.writeText and flips to the copied state".
 describe("CopyButton", () => {
+  beforeAll(() => {
+    // navigator.clipboard only exists in secure contexts; provide a minimal
+    // stand-in when absent so the spies below always have a target.
+    if (!("clipboard" in navigator)) {
+      Object.defineProperty(navigator, "clipboard", {
+        value: { writeText: async () => {} },
+        configurable: true,
+      });
+    }
+  });
+
   beforeEach(() => {
     vi.restoreAllMocks();
   });

vite.config.ts

@@ -62,7 +62,7 @@ export default defineConfig(({ mode }) => {
     test: {
       projects: [
         {
-          extends: "./vite.config.ts",
+          extends: true,
           test: {
             name: "server",
             environment: "node",
@@ -71,7 +71,7 @@ export default defineConfig(({ mode }) => {
           },
         },
         {
-          extends: "./vite.config.ts",
+          extends: true,
           // Pre-bundle the component-test dependency graph: on a cold Vite cache
           // (every CI runner) a mid-run dep-optimization reload can flake the suite.
           optimizeDeps: {