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/wdio.shared.conf.js

@@ -74,6 +74,7 @@ export const sharedConfig = {
     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() works in Mocha non-arrow context — safe for both protocols
       this.skip();
     }
   },
@@ -82,10 +83,13 @@ export const sharedConfig = {
   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);
-      });
+      // Use string script for cross-protocol compatibility (devtools + webdriver)
+      const errors = await browser.execute(
+        'return (function() {' +
+        '  var toasts = Array.from(document.querySelectorAll(".toast-error, .load-error"));' +
+        '  return toasts.map(function(t) { return (t.textContent || "").trim(); }).filter(Boolean);' +
+        '})()'
+      );
 
       const expected = browser.__expectedErrors || [];
       unexpected = errors.filter(e => !expected.some(exp => e.includes(exp)));