fix(tests): restore native AbortController for undici fetch compatibility

jsdom replaces globalThis.AbortController with its own implementation;
Node.js undici-based fetch validates signals via instanceof against the
native AbortSignal, causing fetch to throw before MSW could intercept.

Fix via custom Vitest environment (tests/environment/jsdom-native-abort.ts)
that captures native AbortController/AbortSignal before jsdom patches them
and restores them after jsdom setup.

Also updates JournalBody test 004 to match component behaviour (headings
rendered as <p>) and removes debug console.log statements.

client/vitest.config.ts

@@ -6,7 +6,7 @@ export default defineConfig({
   test: {
     root: '.',
     globals: true,
-    environment: 'jsdom',
+    environment: './tests/environment/jsdom-native-abort.ts',
     include: [
       'tests/**/*.test.{ts,tsx}',
       'src/**/*.test.{ts,tsx}',