feat: unified E2E testing engine — 205 tests, dual-stack support

Infrastructure:
- adapters/: base, tauri (port 9750), electrobun (port 9761 + PTY daemon)
- helpers/: 120+ centralized selectors, reusable actions, custom assertions
- wdio.shared.conf.js + stack-specific configs

18 unified specs (205 tests):
splash(6) smoke(15) settings(19) terminal(14) agent(15) search(12)
files(15) comms(10) tasks(10) theme(12) groups(12) keyboard(8)
notifications(10) diagnostics(8) status-bar(12) context(9)
worktree(8) llm-judged(10)

Daemon: --stack tauri|electrobun|both flag
Scripts: test:e2e:tauri, test:e2e:electrobun, test:e2e:both

tests/e2e/wdio.shared.conf.js

@@ -0,0 +1,113 @@
+/**
+ * Shared WebDriverIO configuration — common settings for both Tauri and Electrobun.
+ *
+ * Stack-specific configs (wdio.tauri.conf.js, wdio.electrobun.conf.js)
+ * import and extend this with their own lifecycle hooks and capabilities.
+ */
+
+import { resolve, dirname } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { getResultsDb } from './infra/results-db.ts';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const projectRoot = resolve(__dirname, '../..');
+
+export const sharedConfig = {
+  // ── Runner ──
+  runner: 'local',
+  maxInstances: 1,
+
+  // ── Connection defaults (overridden per-stack) ──
+  hostname: 'localhost',
+  path: '/',
+
+  // ── Specs — unified set, all shared ──
+  specs: [
+    resolve(projectRoot, 'tests/e2e/specs/splash.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/smoke.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/groups.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/settings.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/theme.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/terminal.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/agent.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/keyboard.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/search.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/notifications.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/files.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/comms.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/tasks.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/status-bar.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/context.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/diagnostics.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/worktree.test.ts'),
+    resolve(projectRoot, 'tests/e2e/specs/llm-judged.test.ts'),
+  ],
+
+  // ── Framework ──
+  framework: 'mocha',
+  mochaOpts: {
+    ui: 'bdd',
+    timeout: 180_000,
+  },
+
+  // ── Reporter ──
+  reporters: ['spec'],
+
+  // ── Logging ──
+  logLevel: 'warn',
+
+  // ── Timeouts ──
+  waitforTimeout: 10_000,
+  connectionRetryTimeout: 30_000,
+  connectionRetryCount: 3,
+
+  // ── Hooks ──
+
+  /** Smart test caching: skip tests with 3+ consecutive passes */
+  beforeTest(test) {
+    browser.__expectedErrors = [];
+
+    if (process.env.FULL_RESCAN) return;
+
+    const db = getResultsDb();
+    const specFile = test.file?.replace(/.*specs\//, '') ?? '';
+    if (db.shouldSkip(specFile, test.title)) {
+      const stats = db.getCacheStats();
+      console.log(`Skipping (3+ consecutive passes): ${test.title} [${stats.skippable}/${stats.total} skippable]`);
+      this.skip();
+    }
+  },
+
+  /** After each test: check for error toasts, record in pass cache */
+  async afterTest(test, _context, { passed }) {
+    let unexpected = [];
+    try {
+      const errors = await browser.execute(() => {
+        const toasts = [...document.querySelectorAll('.toast-error, .load-error')];
+        return toasts.map(t => t.textContent?.trim()).filter(Boolean);
+      });
+
+      const expected = browser.__expectedErrors || [];
+      unexpected = errors.filter(e => !expected.some(exp => e.includes(exp)));
+
+      if (unexpected.length > 0 && passed) {
+        throw new Error(
+          `Unexpected error toast(s) during "${test.title}": ${unexpected.join('; ')}`
+        );
+      }
+    } catch (e) {
+      if (e.message?.includes('Unexpected error toast')) throw e;
+    }
+
+    const db = getResultsDb();
+    const specFile = test.file?.replace(/.*specs\//, '') ?? '';
+    db.recordTestResult(specFile, test.title, passed && unexpected.length === 0);
+  },
+
+  // ── TypeScript ──
+  autoCompileOpts: {
+    tsNodeOpts: {
+      project: resolve(projectRoot, 'tests/e2e/tsconfig.json'),
+    },
+  },
+};