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/src/__stubs__/relicario_wasm.stub.ts

@@ -0,0 +1,13 @@
+// Stub for the runtime-only WASM module. Used by vitest so that modules
+// importing relicario_wasm.js can be loaded in a Node/happy-dom environment.
+// Individual tests that exercise WASM calls should mock the relevant exports.
+
+export default async function init(): Promise<void> {}
+export const unlock = (): never => { throw new Error('wasm stub: unlock not mocked'); };
+export const lock = (): void => {};
+export const manifest_encrypt = (): never => { throw new Error('wasm stub: manifest_encrypt not mocked'); };
+export const manifest_decrypt = (): never => { throw new Error('wasm stub: manifest_decrypt not mocked'); };
+export const settings_encrypt = (): never => { throw new Error('wasm stub: settings_encrypt not mocked'); };
+export const default_vault_settings_json = (): string => '{}';
+export const embed_image_secret = (): never => { throw new Error('wasm stub: embed_image_secret not mocked'); };
+export const register_device = (): never => { throw new Error('wasm stub: register_device not mocked'); };

extension/src/setup/__tests__/setup.test.ts

@@ -0,0 +1,37 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { finishSetup } from '../setup';
+
+describe('finishSetup', () => {
+  beforeEach(() => {
+    (global as any).chrome = {
+      tabs: {
+        create: vi.fn(() => Promise.resolve({ id: 999 })),
+        getCurrent: vi.fn(() => Promise.resolve({ id: 42 })),
+        remove: vi.fn(() => Promise.resolve()),
+      },
+      runtime: {
+        getURL: vi.fn((p: string) => `chrome-extension://abc/${p}`),
+      },
+    };
+  });
+
+  it('opens vault.html in a new tab', async () => {
+    await finishSetup();
+    expect(chrome.runtime.getURL).toHaveBeenCalledWith('vault.html');
+    expect(chrome.tabs.create).toHaveBeenCalledWith({
+      url: 'chrome-extension://abc/vault.html',
+    });
+  });
+
+  it('closes the current setup tab after opening the vault tab', async () => {
+    await finishSetup();
+    expect(chrome.tabs.getCurrent).toHaveBeenCalled();
+    expect(chrome.tabs.remove).toHaveBeenCalledWith(42);
+  });
+
+  it('still opens the vault tab even if closing the setup tab fails', async () => {
+    (chrome.tabs.remove as any).mockRejectedValueOnce(new Error('no permission'));
+    await expect(finishSetup()).resolves.not.toThrow();
+    expect(chrome.tabs.create).toHaveBeenCalled();
+  });
+});

extension/src/setup/setup.ts

@@ -1101,6 +1101,7 @@ function attachStep5(): void {
 
       state.configPushed = true;
       render();
+      void finishSetup();
     } catch (err: unknown) {
       console.error('[relicario setup] register device failed:', err);
       state.error = `Failed to register device: ${err instanceof Error ? err.message : String(err)}`;
@@ -1131,6 +1132,23 @@ function attachStep5(): void {
   });
 }
 
+// --- Completion handoff ---
+
+/// Open the fullscreen vault tab and best-effort close the setup tab.
+export async function finishSetup(): Promise<void> {
+  const vaultUrl = chrome.runtime.getURL('vault.html');
+  await chrome.tabs.create({ url: vaultUrl });
+  try {
+    const current = await chrome.tabs.getCurrent();
+    if (current?.id !== undefined) {
+      await chrome.tabs.remove(current.id);
+    }
+  } catch {
+    // Setup tab may not be closeable (e.g., opened as popup rather than a tab).
+    // The vault tab is open — that's the user-visible success.
+  }
+}
+
 // --- Boot ---
 
 document.addEventListener('DOMContentLoaded', () => {

extension/tsconfig.json

@@ -12,5 +12,5 @@
     "baseUrl": "."
   },
   "include": ["src/**/*"],
-  "exclude": ["node_modules", "dist", "wasm", "src/**/__tests__/**"]
+  "exclude": ["node_modules", "dist", "wasm", "src/**/__tests__/**", "src/__stubs__/**"]
 }

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'],