feat(ext/setup): hand off completion to fullscreen vault tab (P2)

After successful device registration (state.configPushed = true), the
wizard now opens vault.html in a new tab and closes the setup tab.
Both create-new and attach-existing flows funnel through the same
finishSetup() handler. Closing the setup tab is best-effort --
chrome.tabs.remove failures don't block the vault open.

Add src/__stubs__/relicario_wasm.stub.ts + vitest.config alias so
setup.ts can be imported in unit tests without the runtime WASM file.
Exclude the stubs dir from the webpack/tsc build in tsconfig.json.

extension/vitest.config.ts

@@ -1,6 +1,14 @@
 import { defineConfig } from 'vitest/config';
+import path from 'path';
 
 export default defineConfig({
+  resolve: {
+    alias: {
+      // Stub the runtime-only WASM module so unit tests can import setup.ts.
+      '../relicario_wasm.js': path.resolve(__dirname, 'src/__stubs__/relicario_wasm.stub.ts'),
+      'relicario-wasm': path.resolve(__dirname, 'src/__stubs__/relicario_wasm.stub.ts'),
+    },
+  },
   test: {
     environment: 'happy-dom',
     include: ['src/**/__tests__/**/*.test.ts'],