fix: correct typeof comparisons in browser SDK

Fix typeof comparisons that compared against the value `undefined` instead
of the string `'undefined'`. Since typeof always returns a string, comparing
to the value `undefined` made these checks always truthy.

Affected functions:
- isDocument() and isWindow() in BrowserApi.ts now correctly return false
  in service worker contexts where document/window are unavailable
- getCrypto() now correctly throws when crypto API is unavailable
- randomUuidV4() now correctly falls back when crypto.randomUUID is missing

Re-enables the valid-typeof ESLint rule to catch this class of bug.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: joker23

.eslintrc.js

@@ -27,7 +27,7 @@ module.exports = {
     'eqeqeq': ['error', 'always', { null: 'ignore' }],
     'prefer-const': ['error', { ignoreReadBeforeAssign: true }],
     'no-var': 'error',
-    'valid-typeof': 'off',
+    'valid-typeof': 'error',
     'no-restricted-syntax': [
       'error',
       { selector: 'ForInStatement', message: 'Use Object.{keys,values,entries} instead.' },

packages/sdk/browser/src/BrowserApi.ts

@@ -5,11 +5,11 @@
  */
 
 export function isDocument() {
-  return typeof document !== undefined;
+  return typeof document !== 'undefined';
 }
 
 export function isWindow() {
-  return typeof window !== undefined;
+  return typeof window !== 'undefined';
 }
 
 /**
@@ -91,7 +91,7 @@ export function getLocationHash(): string {
 }
 
 export function getCrypto(): Crypto {
-  if (typeof crypto !== undefined) {
+  if (typeof crypto !== 'undefined') {
     return crypto;
   }
   // This would indicate running in an environment that doesn't have window.crypto or self.crypto.

packages/sdk/browser/src/platform/randomUuidV4.ts

@@ -91,7 +91,7 @@ export function fallbackUuidV4(): string {
 }
 
 export default function randomUuidV4(): string {
-  if (typeof crypto !== undefined && typeof crypto.randomUUID === 'function') {
+  if (typeof crypto !== 'undefined' && typeof crypto.randomUUID === 'function') {
     return crypto.randomUUID();
   }
 

packages/telemetry/browser-telemetry/src/randomUuidV4.ts

@@ -94,7 +94,7 @@ export function fallbackUuidV4(): string {
 }
 
 export default function randomUuidV4(): string {
-  if (typeof crypto !== undefined && typeof crypto.randomUUID === 'function') {
+  if (typeof crypto !== 'undefined' && typeof crypto.randomUUID === 'function') {
     return crypto.randomUUID();
   }