fix(e2e): cross-protocol browser.execute() — works with both WebDriver + CDP

Root cause: WebDriverIO devtools protocol wraps functions in a polyfill
that puts `return` inside eval() (not a function body) → "Illegal return".

Fix: exec() wrapper in helpers/execute.ts converts function args to IIFE
strings before passing to browser.execute(). Works identically on both
WebDriver (Tauri) and CDP/devtools (Electrobun CEF).

- 35 spec files updated (browser.execute → exec)
- 4 config files updated (string-form expressions)
- helpers/actions.ts + assertions.ts updated
- 560 vitest + 116 cargo passing

tests/e2e/specs/splash.test.ts

@@ -7,17 +7,18 @@
 
 import { browser, expect } from '@wdio/globals';
 import * as S from '../helpers/selectors.ts';
+import { exec } from '../helpers/execute.ts';
 
 describe('Splash screen', () => {
   it('should have splash element in DOM', async () => {
-    const exists = await browser.execute((sel: string) => {
+    const exists = await exec((sel: string) => {
       return document.querySelector(sel) !== null;
     }, S.SPLASH);
     expect(exists).toBe(true);
   });
 
   it('should show the AGOR logo text', async () => {
-    const text = await browser.execute((sel: string) => {
+    const text = await exec((sel: string) => {
       const el = document.querySelector(sel);
       return el?.textContent ?? '';
     }, S.LOGO_TEXT);
@@ -27,7 +28,7 @@ describe('Splash screen', () => {
   });
 
   it('should show version string', async () => {
-    const text = await browser.execute((sel: string) => {
+    const text = await exec((sel: string) => {
       const el = document.querySelector(sel);
       return el?.textContent ?? '';
     }, S.SPLASH_VERSION);
@@ -37,7 +38,7 @@ describe('Splash screen', () => {
   });
 
   it('should have loading indicator dots', async () => {
-    const count = await browser.execute((sel: string) => {
+    const count = await exec((sel: string) => {
       return document.querySelectorAll(sel).length;
     }, S.SPLASH_DOT);
     if (count > 0) {
@@ -47,7 +48,7 @@ describe('Splash screen', () => {
 
   it('should use display toggle (not removed from DOM)', async () => {
     // Splash stays in DOM but gets display:none after load
-    const display = await browser.execute((sel: string) => {
+    const display = await exec((sel: string) => {
       const el = document.querySelector(sel);
       if (!el) return 'not-found';
       return getComputedStyle(el).display;
@@ -57,7 +58,7 @@ describe('Splash screen', () => {
   });
 
   it('should have proper z-index for overlay', async () => {
-    const zIndex = await browser.execute((sel: string) => {
+    const zIndex = await exec((sel: string) => {
       const el = document.querySelector(sel);
       if (!el) return '0';
       return getComputedStyle(el).zIndex;